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This Book is the property of the 
General Electric Company and must 
be returned to the Assistant General 
Foreman when you leave the Testing 
Department. 



No. 



Instructions 



FOR 



Testing Electrical Apparatus 



Copyright 1914 
by General Electric Company 



GENERAL ELECTRIC COMPANY 

TESTING DEPARTMENT 
SCHENECTADY, N. Y. 



June, 1914 No. Y-435 






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QCU375647 

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TABLE OF CONTENTS 



CHAP. 



PAGE 



Introduction 










4 


1 Testing Equipment 






5 


2 The Use and Care of Instruments 






24 


3 Assembly of Machines for Test 






58 


4 Preparation of Apparatus for Test 


Inspec 


tion 




Wiring; Observations During Operation 




98 


5 Testing Records 




106 


6 Methods of Conducting Standard Tests 






108 


7 Direct Current Generators .... 






136 


8 Direct Current Motors 










157 


9 Alternating Current Generators 










172 


10 Synchronous Motors 










183 


11 Synchronous Converters . 










190 


12 Induction Motors 






/ 




208 


13 Steam Turbines 










227 


14 Marine Engine Sets . 










285 


15 General Electric Test Tracks . 










300 


16 Blowers 










305 


1 < Air Compressors 










314 


18 Voltage Regulators . 










318 


19 Industrial Control Apparatus , 










343 


20 Mining and Industrial Locomotive 


s 








353 


21 Porcelain Insulators 










358 


22 Train Control Apparatus 










360 


23 Projectors ..... 










. 373 


24 Transformer Tests . 










. 383 


25 Calculation Sheets 










. 421 


Nomenclature .... 










. 459 


Index 










. 463 



GENERAL INSTRUCTIONS FOR TESTING 

Introduction 

This book is intended to give a general outline of the methods 
and precautions to be followed in test. Every one making tests 
must become familiar with its contents, and will be held respon- 
sible for carrying out tests in accordance with the methods 
and regulations outlined. If, after reading the description of any 
test, the tester is doubtful about specific points, he should refer 
the matter to the Head, or Assistant Head of the Section for 
further instructions before undertaking the work. 

Instructions regarding wiring, starting, and operating 
machines as given in this book must be followed out carefully 
and conscientiously, and under no circumstances will deviations 
be allowed unless permission has first been received from those 
in authority. The importance of carefulness must be realized 
at the outset, since practically all accidents likely to happen to 
men or apparatus are due to. carelessness or lack of appreciation 
of operating conditions. Any man doing careless work, or taking 
any risks that may have serious results, renders himself liable 
to discharge. No one must handle any wiring, connect or operate 
any switchboard or apparatus unless he is entirely familiar with 
all the conditions having reference to the test. In addition to 
being thoroughly familiar with the contents of this book, every 
one is expected to keep himself informed regarding instructions 
that are issued from time to time by the Heads of the Testing 
Department. Such instructions are posted, when issued, on the 
various section and general bulletin boards provided for that 
purpose. 






CHAPTER 1 

TESTING EQUIPMENT 

Electrical Power 

In order to test apparatus under operating conditions it is 
necessary to provide power at various voltages and frequencies 
so that either direct current or alternating current apparatus 
may be readily operated. Direct current power in the Testing 
Department is obtained either direct from the steam plants in 
the works located in Building No. 13 and Building No. 61, or 
from synchronous motor-generator sets installed in the various 
testing sections, the motors of which operate from the 40 cycle 
alternating current shop system. The regular direct current 
shop circuits furnish power at 125 volts, 250 volts and 500 volts. 
By using other shop generator sets connected in series with the 
above circuits, intermediate and higher direct current voltages 
may be obtained where testing conditions so require. These 
shop generators are commonly known in the Testing Depart- 
ment as "boosters" or "exciters." These generators alone may 
be used for furnishing small and moderate amounts of power 
at variable voltages and where close and variable voltage 
control is required. The regular shop circuits carry a fluctuating 
factory and railway load and, therefore, cannot be relied upon to 
give close voltage regulation. The latter must be used, however, 
wherever large amounts of power are required, in which case the 
voltage regulation must be effected by means of shunt boosters 
in series, the fields being controlled so as to maintain the proper 
terminal voltage. 

Direct current power above 500 volts is used chiefly for the 
testing of high voltage direct current railway motors, and is 
obtained either by boosting the 500 volt shop circuit by an aux- 
iliary generator or by means of a 1200/2400 volt 1000 kw. three 
unit set. In all cases when using a "booster" where it is not 
necessary to have one side of the 1200 volt circuit grounded it 
should be so wired that there will not be more than 600 volts 
between either side of the circuit and ground, since the 500 volt 
shop circuit is permanently grounded on one side. This con- 
dition can be readily obtained by connecting the boosting gen- 
erator to the grounded side of the shop circuit. It must be under- 
stood in this connection that, in all testing work, no ground is to 
be used as a return circuit; that is, all circuits must be metallic. 
The 250 volt shop circuit has a grounded neutral; the 125 volt 
shop circuit is obtained between either side of the 250 volt cir- 
cuit and the grounded neutral. All direct current shop circuits 
are wired through circuit breakers and switches permanently 
mounted on switchboards in each testing section. These circuit 
breakers and switches control the whole power in their section; 
they must, therefore, all be opened whenever power is no longer 
required. 



Each of the principal testing sections is equipped with a 
number of small direct current generators capable of giving a 
variable voltage for testing work which are known as "exciters," 
because they are used frequently for field excitation. These 
generators are direct motor driven, steam turbine driven, 
engine driven, or belted sets. Turbine driven sets consist of a 
Curtis turbine driving one or two generators. When the turbine 
drives two generators, the switchboard is arranged so that 
the two armatures can be connected in series or multiple. 
Belted sets are considered as temporary testing sets and are only 
used in emergency, since their use requires greater care and 
attention. Their operation is also a possible source of danger, in 
consequence of the possibility of slipping or breaking belts, etc. 

When an exciter runs in series with a power circuit in order 
to "boost" or "buck" the voltage the following points require 
careful consideration. Under no circumstances must the source 
of driving power be disconnected while the exciter carries load. 
Therefore, no machine must ever be used in such cases unless it 
is equipped with a speed limiting device in good working order, 
which will automatically open the circuit breaker of its armature 
circuit, should the machine begin to operate at excessive speed. 
Particular care should always be taken to see that all safety 
devices, in operation with such machines, are in good working 
condition before using them. All permanently installed motor- 
generator sets have a speed limiting device and low voltage 
release installed on the motors and generators. These are 
wired in series, so that in case the speed rises suddenly, both 
motor and generator circuit breakers will be automatically 
opened and the set shut down. For the same reason, if the 
power supply from which the sets are driven fails all breakers 
will be opened automatically. On direct current turbine driven 
sets the circuit breaker tripping coils are wired so that, when 
the emergency governor operates, their circuits are broken and 
the breakers in the generator armature circuit are opened. 

Turbine driven generators should not be used to "buck" the 
shop voltage, since engine driven and turbine driven sets rely 
only on their friction and windage losses to prevent their 
speed from increasing when the direct current generator is 
"motoring." 

Measurement of ohmic resistance is one of the most common 
tests and it frequently requires much skill to obtain consistent 
results. Special measuring booths are located in the various 
testing sections, fitted with measuring sets provided with 
D'Arsonval galvanometers. The resistance bridges and resist- 
ances used are especially adapted to the work. The measuring 
sets are supplied with storage batteries to furnish current for 
making the measurements. Care must be taken when charging 
the batteries to see that they are not charged at too great a rate, 
also that a high discharge rate does not last for too long a period. 
Occasionally the battery acid should be tested to see that it 
maintains the proper specific gravity. This test is made by a 
hydrometer. 






In order to prevent vibration, the galvanometers are carried 
on piers, having no connection with the building foundations. 
It is essential that the galvanometers be carefully protected 
from vibration or shock, otherwise, resistance measurements 
cannot give accurate results. 

Alternating current generators and motor-generator sets are 
furnished for generating and converting alternating current 
power at the various voltages and frequencies required in test- 
ing apparatus. Taps, from the 40 cycle alternating current 
shop circuit supplying 110 volts, are located in the principal 
testing sections. These are generally used for supplying power 
for the excitation of high potential testing transformer sets. 
As this power is supplied at a constant voltage of 110 volts, a 
potential regulator is employed with the high potential testing 
transformer, in order to obtain the high potentials necessary for 
the various types of apparatus tested. The wiring arrangement 
of a high potential testing set is shown in Fig. 2. 



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rWVWW-i 




Fig. 2 

WIRING ARRANGEMENT OF HIGH 

POTENTIAL TESTING SET 



The Testing Department uses a 2000 kw. 25 cycle, 13,200 
volt turbine driven generating set located in Building No. 61 
for miscellaneous power tests. From this set power is dis- 
tributed by means of high tension lines to Buildings Nos. 16, 
12 and 114. This set is also used for supplying power to the 
railway at Wyatts Crossing and a considerable amount of 
railway testing is done by its agency. When such work is 
being carried on, an extensive system of high tension lines is 
connected to this machine, consequently the circuit has con- 
siderable capacity. When this circuit is in use, therefore, testers 
should be cautioned not to come in contact with any part of the 
circuit, or with the leads attached to it, since its capacity may 
give rise to a voltage sufficient to produce fatal results. 




Fig. 3 

PLUG CONNECTION BOARD FOR SHOP ALTERNATORS FOR 

CONNECTING A, Y or 2 PHASE 



O Indicates front contact 
° Indicates back contact 



To Connect 


Plug 


Connecting 


A 


A plugs 


5 to 3, 4 to 6, 2 to 1,7 to 8 


Y 


Y plugs 


2 to 1, 3 to 6 to 7 


2<p 


2 <p plugs 


3 to 7, 6 to 1 


3-phase lines =1,2 and 3. 


o i; no , J phase No. 1=1 and 3 (Line Nos.). 
*<p lines ^ phase NQi 2 =2 and 4 (Line Nos-)< 


Remove ALL plugs to remove voltage from outgoing lines. 






No one working on this circuit, or other circuits of high voltage 
in the Testing Department, should approach nearer than 12 
inches to the circuit, because actual contact is by no means 
always necessary in order to receive a dangerous shock. Due to 
high static capacity and other peculiar conditions, it is extremely 
important that the Head of the Section investigate thoroughly 
other sections which have taps to these lines and make sure that 



S 



/ia/f of one phase winding 




Fig. 4 

DIAGRAM SHOWING INTERNAL CONNECTIONS OF PLUG BOARD 

FIG. 3 AND PHASE RELATIONS. PHASE WINDINGS ARE 

PERMANENTLY CONNECTED TO BACK CONTACTS 

AS SHOWN BY NUMERALS 



they are not, and will not be in use, before anyone is allowed to 
operate this machine. This must be done in order that all taps 
may be properly protected when not in use, and also that no 
accidents may occur, due to misunderstandings. No wiring 
whatever should be done on this circuit while it is alive. In all 
cases, tests being operated from this circuit must have oil 
switches interposed between the test wiring and the lines so 
that connections to the lines may be made through these 
switches. Wherever temporary switches become necessary they 
must either be located at such a height or be protected by a 



mechanical barrier so that men cannot accidentally come in 
contact with them. Gil switches, permanently installed in the 
different testing sections for connecting to the lines mentioned 
above, must be kept locked open when power is not being 
drawn from the lines. The Head of the Section is responsible 
for seeing that these matters are attended to. 

Larger amounts of power may be obtained from the three 
unit set in Building No. 61 consisting of an ATI-16-5600-300- 
10,000 volt, 40 cycle synchronous motor driving an ATB 24- 
6250-300, 4000/2300 volt, 60 cycle and an ATB 10-6250-300, 
13,200/6600 volt, 25 cycle alternator. (See page 459 for nomen- 
clature.) By the use of a bank of transformers a wide range of 
voltages may be obtained and distributed to the various testing 
sections. This set is very convenient for taking zero power- 
factor heat runs on large alternators. 

A 1500 kw. three unit set consisting of two MPC 8-750-600, 
250 volt generators driven by a 40 cycle synchronous motor is so 
wired that the two generators may be connected in multiple or 
series for supplying power at 250 or 500 volts. 

In addition to these sets there are others situated in the 
various sections convenient for power or for "feeding back" 
tests or for the conversion of direct to alternating current or 
vice versa. The armature terminals of all alternating current 
generators are connected to high tension switch panels. By 
this means, the armatures, when their windings permit, may be 
readily connected Y or A three-phase, or two-phase. Although 
such switchboard panels are insulated for 15,000 volts, the same 
caution, nevertheless, should be observed in operating them 
as though the lines were bare conductors. The armature coil 
terminals are each marked on the terminal board. One of the 
panels is shown in Figs. 3 and 4. 

Steam Power 

A considerable amount, of steam is used for the testing of 
steam turbines, marine engines and for driving turbine and 
engine driven exciter sets, steam pumps, etc. Steam is supplied 
from power houses located in Buildings Nos. 13 and 61 and is 
conveyed to the Testing Department through underground 
mains in the yards. The steam pipes are placed overhead in all 
buildings. These mains are well lagged with asbestos covering 
and contain a sufficient number of expansion joints to take care 
of all expansion and contraction. Gate valves are located in the 
mains at the boiler houses and also just inside the building in 
which the testing section is located. Motor operated emergency 
valves are installed in the important mains, so that the steam 
supply may be shut off by closing a switch in the testing section. 
Each man working in the steam test should know where these switches 
are located, so that he may be able to close these valves quickly if 
necessity arises. These valves must be regularly tested at least 
once a week to insure certain operation. Steam separators and 
traps are connected in all mains at the proper points to take care 
of condensed water. Steam is distributed from the mains to 

10 



the various section testing stands by leading off pipe branches. 
These branches are of sufficient size to test any machine that 
will be placed in the particular testing stand. At each stand the 
branch steam mains are fitted with two steam valves, viz: a 
special Globe Valve, which may be used to throttle steam 
for machines under test, when necessary, and another valve 
which is never to be used for throttling. This arrangement 
prevents any steam leaking through the branch when not in 
use. Each valve is furnished with a handwheel of sufficient 
diameter, so that no additional leverage should be necessary 
in opening or closing. 

All steam valves must be tightly closed, using the hand- 
wheel fitted to the valve. The handwheel should then be given a 
slight backward turn in order to free the stem sufficiently to 
take care of expansion and contraction. If these precautions 
are observed the valve may always be easily operated by the 
handwheel. Each branch main valve is furnished with a small 
by-pass valve. When it is possible to obtain a sufficient supply 
of steam through these by-pass valves to carry on a test, they 
should be used in preference to throttling with the large valve. 
Drip cocks are in all cases located between the main valve and 
the machine or throttle valve. These drip cocks must always 
be open when steam is not flowing through the main in which 
they are located, and should be left open until steam is flowing 
freely through the main. That is, wherever condensed water can 
collect in dead-ended mains, a drip should be provided to carry 
this water away as fast as it collects, in order to prevent a 
water hammer in the main. A water hammer may produce 
enormous stresses in a steam main, hence great care must be 
taken to prevent its development. If water is likely to 
collect in the main, the supply of steam should be entirely 
shut off and all water must then be removed before re-opening 
the steam valve and attempting to use the main again. 

In each section having large steam mains, there are regularly 
appointed men, whose duty it is to operate all valves with the 
exception of the throttle valve at the machine under test. 
The tester should, therefore, ask these men to operate any valve 
except the throttle valve, which may be operated by the tester 
himself. Small by-pass valves should also be used in every case 
gradually to warm up a steam main before allowing steam to 
flow into it through the opening of the main valve. By using the 
by-pass valve in this manner, with all drips open, the main can be 
gradually brought to its running temperature, after which the 
large valve giving the full flow of steam may be opened. 

All exhaust steam piping is arranged to permit the exhaust 
steam being passed into the heating system of the factory, 
into the atmosphere direct, or into surface condensers. Wher- 
ever possible, condensers should be employed in order to 
economize steam. Whenever steam heat is required, however, 
exhaust steam may be passed into the heating system. Steam 
should only be exhausted into the atmosphere direct in excep- 
tional cases where it cannot be utilized as just mentioned. 

11 



Shop Motors and Generators 

The Testing Department equipment includes a large number 
of 125, 250, and 500 volt direct current machines of various sizes, 
which are always available for driving generators under test. 
They can also be used as a load for motors receiving test, in 
which case they are run as generators. Many of these machines 
are shunt wound; a large number, however, are provided with a 
series field winding and also with commutating poles. Ordi- 
narily when using such machines as motors, they are operated 
as shunt machines. Sometimes, however, these motors have 
to operate in multiple and it is then necessary to use a certain 
proportion of the series field on one machine in order to give 
the proper speed equalization. Such cases, however, are special 
and definite instructions should be obtained before operating 
the combination. 

When operating as motors, machines should never be sepa- 
rately excited, unless the test requirements so demand. In such 
cases, precautions must be taken to prevent loss of motor field, 
due to the fields being excited from one source and the armatures 
from another. When shop machines are operated as motors 
they must have the speed limiting switch mounted on the shaft, 
connected to the trip coils on the breakers placed in the armature 
circuit, so that in case a motor begins to run too fast it will 
automatically be shut down. 

When using direct current machines as compound wound 
motors, the following precautions must be observed. The series 
fields must not be connected differentially. They must have 
only sufficient series field to give the required regulation. Should 
excessive series field be used and the shunt field adjusted under 
full load conditions to give normal speed at normal load, the 
speed may rise to a dangerous point if the load falls suddenly. 
When machines are so used great care should be exercised in 
operation to prevent any condition occurring which may give a 
dangerous rise in speed. When such special conditions occur 
it must be clearly understood that some one man connected 
with the test must watch the machine continuously. He is 
responsible for seeing that accidents, due to excessive speed, 
cannot occur. 

In all cases the general condition of machines, especially the 
condition of commutators, brushes, bearings, etc., must be 
frequently and carefully noted and any defects reported to the 
Head of Section. 

When using the shop apparatus, it is as important to take 
the same precautions in wiring and starting for test as are taken 
in the case of the apparatus for production. These precautions 
are detailed in the following pages. 

Several of the shop motors used by the Testing Department are 
alternating current synchronous motors. In most cases, these 
are permanently connected to a direct current generator. It is 
often necessary, however, to erect and operate synchronous 
motors temporarily for production tests. 

12 



When starting a synchronous motor the precautions must be 
observed that are explained in Chap. 11. They must always be 
run at unity power-factor, unless the special requirements of the 
test are such that this cannot be done. Since the greater number 
of these motors are occasionally operated under variable loads, 
the value of the field current should be watched to see that the 
armature current is of the proper value for unity power-factor. 
Should a motor fall out of synchronism, in consequence of exces- 
sive overload, or otherwise, the armature circuit must be opened 
immediately to prevent injury to the winding from overheating. 
When shop generators and motors are being used the lubrication 
of their bearings must always be inspected at starting and also 
at definite intervals during operation to keep the bearings cool 
and prevent overheating. In addition, the instructions on bear- 
ings given later must be observed. 

Safety Devices 

In a department such as the Testing Department it is 
essential that proper guards be used in all cases which might be 
considered as in any way likely to be the cause of an accident. 
With this in mind special testing equipment which is referred to 
in other pages of this book has been furnished. Under no cir- 
cumstances should switches, circuit breakers or other controlling 
devices be used which are not properly equipped with handles, 
washers, etc. There is in each testing section a stock of these parts 
and the Head of Section is responsible to see that none of these parts 
is missing. 

All circuits, whether high potential or low potential, which are 
installed permanently are marked so that all can be identified 
at any time. With very few exceptions current transformers must 
be used as a matter of safety when taking measurements on high 
potential circuits. W T henever a connection is made to permanent 
circuits, proper protection must be afforded by oil switches, cir- 
cuit breakers or contactors. 

All shaft extensions which are exposed must be guarded. All 
couplings and belts must be guarded either by a permanent fence 
constructed of pipe work, or a portable fence designed for this 
purpose. 

Speed limiting devices (see page 113) must be installed on all 
shop apparatus in which excessive speed is possible and should 
be adjusted at least once a week to operate at 10 per cent above 
normal speed. Whenever speed limiting devices cannot be per- 
manently installed they must be used temporarily. 

Safety valves and atmospheric relief valves are also per- 
manently located wherever necessary on permanent steam 
piping. They should be installed whenever necessary on tem- 
porary piping in order to insure safety. Great care must be 
taken in locating these devices in reference to steam mains, air 
compressor work and air tanks. The tests and apparatus given 
above are vitally important for the safe* operation of the testing 
equipment, and the Head of the Section must insist that they 
be closely followed. 

13 



Switchboards and Floor Stands 

Section switchboards are connected to the permanent wiring 
to obtain flexibility. These are so designed as to minimize the 
amount of temporary wiring as much as possible. The switch- 
boards are of two classes; viz. those connected to high voltage 
circuits (above 600 volts), and the low voltage switchboards 
(600 volts and below). 



^LrnmW^^ 9 ^^ 



Mfti&itfiffr fllfMft ^afe tfiftrl 



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Fig. 5 
FRONT OF HIGH TENSION SWITCHBOARD, PLUG TYPE 



The high voltage switchboards consist of a number of slate 
panels provided with high tension insulators, to which the 
permanent wiring terminals are attached leading from the 
permanently installed alternating current generators, trans- 
formers, and "floor stands." At some distance behind the 
slate front of the board, a second set of high tension insulators 
is carried on an iron frame, which are also fitted with terminals 
connected to horizontal busses running throughout the length of 
the board. Since with this arrangement, generators, floor stands, 
and transformer terminals are located in vertical lines, whereas 
busbar terminals are located horizontally, it is possible to pass from 
one panel to any other panel on the board by inserting switches 
between the front and back sets of terminals. The metallic 
terminals used on these boards form the contact points for plug 
switches. These plug switches are designed so that having 
removed or inserted a plug, all live parts are thoroughly 
protected. 

14 



No plug switch must be used for connecting or disconnecting 
the front and back systems of contacts if there is any voltage on 
them. The switching system must be considered merely as a transfer 
scheme and must always be operated as such. 



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It will be readily seen by referring to Fig. 5 and to 
diagram, Fig. 6, that great flexibility is obtained, since any 
generator connected to a switchboard may be readily trans- 
ferred to any "floor stand" or to any bank of transformers. 
Furthermore, any "floor stand" may be immediately connected 



15 



with any other "floor stand" by merely inserting plug switches 
at the board. 

"Floor stands" are so located in each testing section that 
all high voltage apparatus may be installed near them, thus 
reducing to a few feet the length of high tension cable which is 
required for the machine in test. The "floor stands" carry dis- 
connecting switches and oil switches, through which the final 
connections can be made between their terminals and the 




Fig. 7 
FRONT OF HIGH TENSION FLOOR PANEL 



terminals on the high tension switchboard panel. One of these 
stands is shown in Figs. 7 and 8. 

Green and red "tell tale" lights are located on all switch- 
board panels and also on the "floor stands." They are auto- 
matically operated whenever an oil switch on the "floor stand," 
or a plug switch on the switchboard is opened or closed. When a 
red lamp is burning either at the "floor stand" or on the switch- 
board panel, it indicates that the terminals are in use, and 

16 



connected to another circuit. If red lights are burning, it is, 
therefore, necessary to investigate carefully all panel con- 
nections before making any changes. When, however, a green 
lamp is burning it indicates that the panel, or "floor stand," is 
free, and may therefore be used. For example: A red light 
burning on the "floor stand" indicates that the oil switch has 
been closed on the corresponding "floor stand" panel and that 




Fig. 8 

HIGH POTENTIAL FLOOR STAND SHOWING 

INTERIOR WIRING AND CONSTRUCTION 



the terminals of the "floor stand" panel are alive. Again, if a 
red light is burning on the "floor stand" its switchboard panel 
has been connected by the plug switches to another panel, 
consequently, the "floor stand" terminals may be alive. Hence, 
the red light acts as a danger signal. It should never be entirely 
trusted, however, and the same care should always be taken 
as though "tell-tale lights" did not exist. 

17 



Ais 




Fig. 9 
HIGH POTENTIAL PEDESTAL AND TESTING TABLE 



Connections are brought out at the top of the "floor stands" 
through high potential bushing insulators to terminal blocks 
mounted on the insulators. All this wiring is permanent. 
From the terminal blocks, temporary lines must be run to 
the high potential testing table. A second row of insulators is 
provided on the top of the "floor stands" which must be used 
only as strain insulators. The temporary cables running to 

18 



the testing table must be securely fastened to these insulators. 
By this means the strain on the connections at the terminal 
blocks is relieved and wires cannot drop to the floor if they 
become disconnected. The insulators are arranged so that 
cables can be taken off at any angle with a safe distance between 
them. 

If temporary wiring has to be carried some distance, high 
potential pedestals must be used to support the spans as shown 
in Fig. 9. 

The testing table shown in Fig. 9 is the standard type of 
high potential table used in the Testing Department. These 
tables are constructed so that all high potential wiring is pro- 
tected, and it is impossible to make contact with it when the 
table is in use. High voltage and low voltage circuits within 
the table are placed in separate compartments and insulated 
from each other. Tables are built of asbestos, wood, angle 
iron and expanded metal. The a-c. compartments contain 
an oil switch, potential transformers, and current transformers. 

High voltage connections are made at the top of the table 
as on high potential "floor stands." The secondaries of the 
current and potential transformers are connected to binding 
posts in their respective compartments, forming the terminals 
of the permanent wiring leading to the instruments on the 
front or operating side of the test tables. All current trans- 
formers should have a capacity of 5 amperes for the secondary. 
Transformer secondaries should be kept grounded on one side 
when in use. A detailed print of the wiring circuit will be found 
mounted on each table. All instrument switches and terminals 
are properly and plainly labeled. All table wiring is permanent 
and insulated for a maximum working voltage of 15,000. 

The d-c. compartment is wired for all the circuits of two 
d-c. machines for voltages not exceeding 600 volts. The table 
is furnished with double-pole 500 ampere 600 volt circuit 
breakers. For all currents above 300 amperes, terminals are 
provided for the standard ammeter shunts used in the Testing 
Department. When using currents above 500 amperes the 
circuit breaker on the table must be cut out of circuit and 
breakers of larger capacity wired in the circuit external to 
the table. When direct currents are read direct, ammeter jacks 
are provided which allow the insertion or removal of the instru- 
ment in circuit without interrupting the circuit. 

Though these tables are fitted with safety devices and interlocks, 
etc., in order to render all protection possible, operators must 
treat them as if no protection exists. In other words, great attention 
must be given to all details of operation, and in no case should 
connections be changed by throwing switches, etc., unless the 
operator feels certain of the correctness of so doing. 

All d-c. switchboards recently installed are of the plug 
terminal type, but they differ radically from the a-c. plug 
boards. The older d-c. boards are equipped with bolted termi- 
nals. Figs. 10 and 11 show the front and back views respec- 
tively of a direct current switchboard of the plug type. These 

19 



boards carry terminals, circuit breakers and switches for all 
d-c. shop circuits. Switchboards are interconnected with 
each other and by means of underground cables are connected 
to small "pit switchboards" or "posts" or "floor stands' 
conveniently located. These are generally fitted with plug 
terminal connections, and are connected permanently to the 
d-c. switchboards. All exciter sets are also connected to the 
d-c. switchboards. Hence, any "stand," "pit," "exciter,' 
etc., can be readily connected to any part of the test desired. 




Fig. 10 
FRONT OF D-C. SECTION SWITCHBOARD 



In making connections on any of the "plug boards" plugs 
must not be allowed to strike the slate panels and chip or crack 
them. See what connections are required, then carefully insert 
the plug in its receptacle, entering it to the locking position. 
If these precautions are taken the least damage will be done 
in case of short circuit. The ampere rating of each switch- 
board terminal is placed above it. No cables or terminal must 
be overloaded. 

All field plugs must be carefully locked on insertion so 
they cannot accidentally be pulled out. 

All "pits" and "stands" must be kept clean and free of 
rubbish. 

Cables with defective insulation or having defective plug 
terminals must not be used, but must be sent by the Head of 
Section to the repair shop as soon as the defect appears. All 
cables must be kept on cable racks when not in use. 

The following example illustrates, the general procedure to be 
followed in the wiring of high voltage alternating current circuits. 
To connect a shop alternator to a high voltage machine on the 
testing floor near the high potential "floor stand," see that the 
oil and disconnecting switches are open, then connect . the 
alternator, at the armature terminal board, to give the proper 
voltage and phase combination. Connect the machine by 
temporary wiring to the high potential terminals on the "floor 

20 



stand." When the machine is ready to start, a transfer bus should 
be selected which is not in use on the high potential switch- 
board. The alternator armature should then be plugged in on 
the transfer bus, after noting that the alternator oil switch is 
open. Next plug the panel connected to the proper floor stand 
to the same bus, and close the alternator oil switch. On closing 
the circuit at the "floor stand" panel, a red lamp lights up and 
indicates that the connection of the alternator has been made 
up to this point. The disconnecting switches should then be 




Fig. 11 
BACK VIEW OF D-C. SECTION SWITCHBOARD 

closed at the "floor stand." Finally, the oil switch on the "floor 
stand" should be closed and a red light burns on the correspond- 
ing panel of the high potential switchboard, showing that the 
panel is connected through the high potential "floor stand" to 
the circuit. The oil switch in the test table must be employed to 
open and close the high tension circuits, if required during the 
test. In all cases oil switches should be used to "make" or 
"break" alternating current circuits, where such circuits carry 
an appreciable amount of current. 

In all high voltage work proper precautions should always be 
taken to insure against accident in handling circuits. In all cases 
where temporary circuits of high voltage are used, they must be 
thoroughly protected by mechanical barriers and danger signals; 
and white tape should be used wherever it is advantageous as 
an additional warning. 

Water Boxes 

It is often necessary in testing to dissipate electrical energy 
through a resistance. When it is necessary to use resistances 

21 



as a load for large machines, the water box has been found 
most convenient. The water box, as used in the Testing Depart- 
ment, is an iron box mounted on porcelain insulators. Suspended 
above the box by insulators is a triangular iron blade which 
can be lowered into the box. When the water box has been 
filled and the resistance adjusted by the addition of salt, the 
resistance may be varied by lowering or raising the plate in 
the liquid which is admirably adapted to close adjustment. 

The box is mounted on porcelain insulators; it should, 
however, always be considered as grounded. In connecting 
the boxes to grounded shop circuits, the grounded side should 
be connected to the cable leading to the box, and the ungrounded 
side should be connected to the plate. When using water 
boxes as a load on three-phase circuits, the cables leading from 
the box should be connected together to form a Y connection, 
and the phase cables should be connected to the plates. 

Before loading a machine on a water box, the salt solution 
must be adjusted for the voltage and current required. To 
do this, apply a low voltage to the box and note the 
current. If this is not possible add fresh water to the 
solution until the resistance is sufficiently high to prevent 
an excessive rush of current when the bottom of the plate 
enters the solution. 

The majority of water boxes in the Testing Department 
are equipped with hydraulic cylinders for operating the triangular 
plate. These consist of vertical cylinders fitted with a piston 
and piston rod from which the plate is suspended. Water 
is forced into the cylinder, or released from it by two electrically 
operated valves, one for raising, and the other for lowering 
the plate. Small cables run from the electrical valves to a 
small distributing switchboard, whence leads may be carried 
to any of the testing tables, and connected to operating switches. 
Water boxes can be operated from any section by this method 
of remote control. If it is desired to operate water boxes in 
multiple, the cables leading to the control valves must be 
connected in multiple, and a single operating switch will control 
any number of boxes. 

Unless special permission has been received more than 
2300 volts must not be connected to water boxes unless they 
are specially insulated. 

The standard water box used will dissipate 75 kw. continu- 
ously without excessive heating. If the water in the boxes is 
allowed to boil, the resistance regulation becomes very unsatis- 
factory. Arcing may then occur and set up electrical surges. 
Hence, the temperature of water boxes must always be kept 
well below the boiling point, either by allowing cold water to 
run into them continuously while under load, or if necessary 
by reducing the load. 

To prevent arcs and therefore excessive voltage rises, 
water boxes must never be used to open alternating current 
circuits. 

22 



Field Rheostats 

The Testing Department is equipped with many wire resist- 
ance boxes of small and moderate current capacity. These 
resistances are not grounded upon the frame, but should always 
be so treated in order to insure safety and freedom from accident. 
For this reason, the frames should always be insulated from one 
another and also from ground. All rheostats are marked with 
their resistance and maximum current carrying capacity, so 
that the proper resistance for a test can be readily selected. 
Defective rheostats must never be used in test, but must im- 
mediately be sent by the Head of the Section to the repair shop. 
Permanent motors are generally equipped with their own starting 
resistance. When starting motors for test, series resistances of 
large current carrying capacity must often be used. In such cases 
the water box is the best type of resistance. When starting 
motors with a water box the voltage drop across the box 
must be reduced to a small value before the motor is thrown 
directly across the line. 

Transformers 

Each test section is equipped with permanent transformers. 
Additional transformers are also available for special tests, 
or for use when the regular transformers are in operation. Per- 
manently installed transformers should be used whenever 
possible to save wiring cost and time and to obtain the advan- 
tages and safety afforded by permanent wiring. On the per- 
manent banks of transformers the primary and secondary termi- 
nals are brought out to terminal boards with- the plug switches 
for making the various transformer coil connections required 
with the cables leading to and from the bank. The primary 
terminal boards are insulated for 15,000 volts between 
lines, and any combination ordinarily desired can be obtained 
by inserting plugs in the proper terminals. The plug switches 
must be considered only as a ready method of connecting up 
the transformer coils. They must not be used for connecting 
or disconnecting live circuits. The boards are thoroughly insu- 
lated, but must always be treated as unprotected, when high 
voltages are used. 

The secondary coils are connected to a low tension plug 
type switchboard where they may be connected by plug ter- 
minals to cables running to any part of the test. Each plug 
terminal is labeled so that no wrong connection should be 
possible, if ordinary care is observed. 

If temporary transformers are used, they must be properly 
installed and wired so that safe operation is secured. All cases 
must be grounded by substantial ground wires or cables, the 
case and ground terminals must be in good condition and fitted 
so that they cannot work loose. Never sit or stand on the top 
of a transformer when connecting or disconnecting it. Always 
use step ladders for this purpose and see that the transformer is 
not alive before touching its leads or terminals. 

23 



CHAPTER 2 

THE USE AND CARE OF INSTRUMENTS 

Care of Testing Instruments 

All measuring instruments for testing work must be obtained 
from the general instrument room, or from branch instrument 
rooms located in several of the testing sections. The instruments, 
while in this instrument room, are in the charge of a man who 
is responsible for their condition and calibration before they are 
given out for testing work. When instruments are taken 
from the instrument room by the tester he must receipt for 
them to the man in charge of the instrument room, and be 
responsible for the proper use and care of them. In all cases, 
the man signing for testing instruments must be responsible 
for their return to the instrument room in as good condition as 
they were received by him. In case instruments are damaged, 
a report must immediately be made out by the man in whose 
charge they are and turned in with the instruments to the man 
in charge of the instrument room. 

All instruments are provided with a mirror under the needle. 
To eliminate parallax and obtain the correct reading, sight the 
needle when it exactly covers its mirror image, then without 
altering the position, read the intersection of the needle with the 
inner scale circle. It should be remembered that while the scale 
on most d-c. instruments is equally divided, so that the errors 
of observation are nearly the same in actual amount in all parts 
of the scale, the percentage error varies inversely with the 
deflection. Therefore, when accuracy is required the instrument 
must not be read at a low point on the scale. 

Before using any instrument it should be carefully inspected 
to determine whether the needle is free and rests at zero. No 
instrument which sticks at any part of the scale should be used 
nor should an instrument be used which has a zero error. In- 
struments containing permanent magnets should not be carried 
through strong magnetic fields, as the accuracy of the instru- 
ment is liable to be affected. 

Nearly all instruments have polished steel pivots and jeweled 
bearings; dropping the instrument on the table or striking it 
against another instrument will injure these pivots, causing the 
needle to stick. 

Curves and certificates should be at hand for correcting the 
instrument readings before starting a test. 

These precautions apply in general to the use of electrical 
instruments, but do not include all the precautions which 
must be taken. Intelligence must always be used when using 
instruments and measuring devices. Precautions which apply 
especially to certain types of apparatus will be noted in the 
following pages referring to various instruments employed. 
It must be noted that, while the metallic case of a testing instrument 
is presumably insulated from the terminals and current carrying 

24 



parts, it may become accidentally grounded. When using such 
instruments, therefore, on high potential circuits, the tester should 
always remember that this condition may occur. He should con- 
sider that the case is at the same position as its terminals. He 
should never touch the metallic cases of instruments when they are 
connected to high potential circuits. If it becomes necessary to tap 
an instrument case to see if the needle is sticking, small insulating 
rods must be used. Lead pencils must not be used. 

Phase Rotation Indicator 

The general form of phase rotation indicator is shown in 
Fig. 12. 

It consists of a laminated iron ring with four windings 
about 90 deg. apart. 

For two-phase, all four windings are used, while for three- 
phase but three are used. The terminals are stamped 1, 2, 3, 4, 
and should be connected to corresponding terminals on the 
a-c. machine under test. These indicators are intended to run 
from the residual magnetism of the machine. 




Fig. 12 
PHASE ROTATION INDICATOR 

The rotor consists of a bar pivoted at the center. This 
bar should rotate in the same direction as the machine under 
test. While this is the general principle of the indicator, there 
are several forms used in the department. They should all 
be operated, however, from the residual magnetism of the 
machine. 

The above sketch shows the general construction of the 
indicator. The phase angles are not absolutely correct but are 
sufficiently accurate for practical purposes. 

The Compass 

The compass or magnetic needles used for indicating polarity 
are of the ordinary commercial type. This instrument is not 
used very frequently in the testing department since there is 
danger of its polarity being reversed in strong magnetic fields. 
Care must therefore be taken when using it. 

25 



Steam Engine Indicators 

Steam engine indicators are of the standard commercial 
type and are used to take indicator cards generally oh marine 
engines. The following points must be considered: The con- 
necting cord must not stretch, the indicator cylinder must 
move freely, the paper must be smooth and held firmly on the 
cylinder, and the pencil must mark plainly and move freely. 

The size of spring used in the indicator must be selected 
so as to give as large a card as possible. Generally speaking, 
the larger the card the more accurate the results. The spring 
must be kept in good condition and must be frequently calibrated 
in order to insure accurate results. 

A Planimeter should be used to measure the area of indicator 
cards. 

In using it always set the vernier and scale at zero. The 
pivot point should be securely located and the tracer moved in 
one direction around the indicator card back to the starting 
point. The roller wheel should roll on a flat unglazed surface 
to secure accurate results. 

Balances and Scales 

In using balances and scales the no-load position should 
always be noted, as a zero error may exist. Always hold bal- 
ances, when measuring, by the hook at the top. After using 
platform scales the beam should always be either dropped or 
locked to avoid damage to knife edges, which a blow may other- 
wise cause. All scales and balances used for important readings 
must be frequently checked against standard weights in order 
to insure accuracy. 

Manometers and Anemometers 

Manometers are used for measuring low air pressures, i.e., 
up to 4 or 5 ounces. For measuring pressures up to 2 ounces 
they consist of two vertical cylinders located parallel to each 
other upon a proper base through which a connection is made 
from one leg to the other. The cylinders or "legs" are partially 
filled with water. In some cases the two legs have a cross 
section ratio of 10:1. When pressure is applied above the 
water in one leg the water is forced downward and the water 
in the other leg rises a corresponding amount. Hence, when 
the cross section of the legs is the same the pressure is equiva- 
lent to the difference in level between the water in the two 
legs, whereas if the ratio of cross sections is 10:1, a water rise 
in the small leg will measure a pressure equivalent to a water 
column 1.1 times the height read. Such an arrangement per- 
mits of accurate observation of pressures. The difference in 
water levels is generally read on a "hook" gauge provided with 
a properly arranged screw and corresponding scales. 

The common " U " tube, consisting of a glass tube bent in the 
form of a letter "U" is frequently employed. One side of the 
tube carries a scale, by which the difference in height of water 
in the two legs can be read. In all cases the zero point must be 

26 



carefully noted, before applying pressure. This reading must 
be added or subtracted, as the case may be, from pressure 
readings. 

Anemometers are used to measure the velocity of air. 
Such meters are not very accurate even at their best and must 
not be used where accurate results are desired. In such cases 
the calibrated orifice or "pitot" tube method of making air 
measurements must be employed. 

Pressure and Vacuum Gauges 

Pressure gauges must not be subjected to extreme heat, 
because their accuracy will be affected. With steam pressure 
gauges, "U" shaped or circular loops must be used in the 
pressure pipes leading to the gauge. These form a trap that 
holds sufficient water to fill the operating spring of the gauge, 
thus protecting it against the high temperature of the live 
steam and keeping it comparatively cool. Vacuum gauges also 




Fig. 13 
SLIP INDICATOR 

must not be subjected to extreme heat. All gauges must be 
regularly checked with standards to make sure they are correct 
when used on important work. 

The Hydrometer 

The hydrometer is used to measure the specific density of 
liquids. It is used in the testing department in connection 
with storage batteries to insure that the electrolyte is kept at 
the proper density. 

Slip Indicator 

Measurement of the slip of an induction motor at any 
load is made by means of a slip indicator such as is shown in 
Fig. 13. This slip indicator is a convenient arrangement for 
comparing mechanically the angular velocities of two shafts, one 

27 



of which is driven at a constant speed by the synchronous motor 
of the slip indicator and the other at the speed of the motor 
under test by means of a flexible coupling between them. 

The indicator is mounted on an iron base, fitted with a 
handle at each end, for carrying or handling it. The synchronous 
motor is very simple in construction. It has a bipolar stator, 
and a four-pole rotor without winding. The shaft carries a 
fly-wheel on one end and on the other a 32 tooth brass gear 
wheel, which may be made to mesh with any one of a nest of 
seven gears, mounted on a parallel shaft, by shifting the motor 
on the brass plate. By loosening two screws passing through 
slots in the sole plate of the motor, the latter may be shifted 
to any desired position, exact alignment being secured by dowel 
pins. The various gears are provided to enable the synchronous 
motor to drive the parallel shaft at different speeds, thus adapt- 
ing the instrument for testing motors with various numbers 
of poles. 

The parallel shaft is equipped at its other end with a bevel 
gear wheel meshing with two pinions of a differential gear. 
Meshing with these pinions on the other side is another bevel 
gear, carried on a shaft the other end of which carries the flexible 
coupling by which it is connected to the machine in test. A 
short auxiliary shaft behind the differential gear has, on one 
end, a gear wheel meshing with the large wheel of the differential 
gear, and on the other end a small handwheel by which to 
hold this shaft. 

A clutch, operated by a lever, connects the auxiliary shaft 
to a cyclometer which registers the number of revolutions of 
the auxiliary shaft. The gear ratio makes one revolution of 
the auxiliary shaft equal to one-half revolution of the differential 
gear. 

The indicator is used as follows: 

With the voltage normal and the speed of the alternator 
held constant at normal frequency of the motor, the indicator 
is connected to the induction motor shaft by means of a "split 
tip." The bevel gear, on the shaft carrying the split tip, is 
driven at the speed of the induction motor. By holding the 
large gear of the differential stationary by grasping the hand 
wheel on the auxiliary shaft, the synchronous motor is mechani- 
cally brought up to the speed of the induction motor by power 
transmitted through the other side of the differential and the 
nest of gears. On closing the line switch on the synchronous 
motor it will immediately fall into step with the alternators 
and run at synchronous speed. Should it fail to do so on 
the first trial, a second or third trial in the same way will 
usually be successful. With the synchronous motor running 
and driving one bevel gear of the differential at synchronous 
speed, and the induction motor driving the other bevel gear 
at the speed of the induction motor, the large gear of the differen- 
tial will rotate and drive the auxiliary shaft and cyclometer. 
In this way, the difference between synchronous speed and 
the speed of the induction motor is mechanically recorded, 

28 



and it is only necessary to read the cyclometer for some definite 
length of time (usually one minute) "to know the exact number 
of revolutions by which the two speeds differ. 

In Fig. 13 the gear wheel of the synchronous motor shaft 
is shown meshed with the gear wheel of the "nest" having the 
same number of teeth (32). adapting the indicator to test a 
four-pole induction motor, since the rotor of the synchronous 
motor has four poles. The other gears of the "nest" have 




Fig. 14 
STATIONARY TORQUE RECORDER 

16, 48, 64, 80, 96 and 112 teeth, respectively, providing for 
testing induction motors with the various numbers of poles, 
commonlv built. 



Stationary Torque Recorder 

Some alternating current motors have a starting torque 
which varies considerably according to the position of the rotor 
at starting. In many cases, therefore, the variation of starting 
torque at different rotor positions must be measured. 

29 



This information can be most satisfactorily obtained by 
using a graphic recording torque meter. Fig. 14 is a sketch of an 
instrument that is successfully employed in the Testing Depart- 
ment for quickly and accurately obtaining this torque. In 
this sketch G represents a form of lever commonly used. It is 
clamped around the pulley or the shaft of the motor under test. 
A wooden disk H is provided, of triangular cross section radially. 
On its conical surface a series of }/% in. grooves is located to 
accommodate the cord K. This cord rotates the drum £ of a 
steam engine indicator on which a record of the variations in the 
torque is traced. The post A supporting the indicator is hollow, 
and a rod connected to the lever B at the lower end and bearing 
against the spring of the indicator, transmits any movement of 
B to the spring, and in turn to the pencil bearing upon the drum. 
The lever B is provided with a number of holes so that it can be 
attached to the stirrup R at various distances from the fulcrum 
S, by which means different leverages can be secured. By this 
adjustment, and by clamping the complete apparatus to the 
levqp: arm at different distances from the motor shaft, the 
maximum travel of the recording pencil on the drum can be 
kept within the limits normal for the indicator spring used. 
The shaft and crank F are supported at right angles to the lever 
B by an iron pipe frame not shown in the sketch. The spring 
balance L is used only in calibrating the apparatus and is then 
disconnected and the rope Z connected directly to the stirrup R. 
The calibration of this instrument should be made as follows: 
With no tension on the rope, pull the cord K and revolve the 
drum E, thus recording the zero line on the paper record. Raise 
the outer end of the lever above the horizontal position and with 
the cord K in that groove on H which gives the proper rotation 
to the drum E, slowly lower the lever by means of the crank F to 
a position considerably below the horizontal plane passing 
through the axis of the motor. This line gives the value W — F. 
Where W is the weight of indicator lever arms, etc., tending to 
rotate the rotor and F is the friction of the motor bearing. The 
lever is now slowly raised to a position correspondingly above 
the horizontal plane and a third line obtained on the indicator 
drum, measuring the value W-\-F. The lever is now blocked 
and held in a horizontal position and the crank F turned until 
the spring balance reads 10 lb. By means of a cord, the drum 
is rotated and a line drawn upon it correspondingly to 10 lb. pull. 
This may be repeated and the indicator card calibrated through 
the range required. 

After the indicator calibration record has been made the 
spring balance, is removed and the rope Z connected directly to 
the stirrup R. Having determined the direction of rota- 
tion of the motor when supplied with power, the line switches 
may be closed, using about one-half normal voltage on the 
motor. By means of the crank F and the rope Z the lever arm is 
rotated through an arc equal to that employed in obtaining the 
friction curve and a record made. Make a similar record while 
lowering the lever through the same arc. While the lever is 

30 



ascending, the record measures the value W-\- F-\-T, where T is 
the torque of the motor under test ; % descending, the record gives 
W — F-\-T. From the five curves* so obtained, the torque at 
any position is readily obtained. 

On these motors the cycle of torque variation usually repeats 
itself regularly during a revolution. It is, therefore, only nec- 
essary to continue the record throughout one of these cycles. 
The indicator card has blanks for recording the machine rating, 
number, and all other information necessary in connection with 
this test. These cards should always be filled out clearly before 
being sent to the Calculating Department. 

The Ballistic Galvanometer 

The Ballistic Galvanometer when used to measure magnetic 
flux or electric quantity must be supported on a pier to elim- 
inate vibration. It may be located either beside the apparatus 
under test, if a pier is available at that place, or at a distance, 
usually in the laboratory. 

In measuring magnetic flux an exploring coil, usually of a 
few turns only, is employed enclosing the flux at any convenient 
point. As the exploring coil voltages are ordinarily very low, 
no particular care is required for insulation except to guard 
against mechanical abrasion. 

The method for obtaining the necessary change of flux may 
be either by withdrawing an exploring coil, by reversing the 
current producing the flux, or by making or breaking the current. 
For permanent magnets the first is the only way possible. 
For electromagnets the second method is the more usual, the 
exploring coil being wound permanently in place. If the current 
is broken without reversal, the measurement is subject to an 
error due to residual magnetism; which in a continuous iron 
circuit (no air gap, as in a stack of ring punchings) sometimes 
gives a remainder of over three-quarters of the whole flux (as 
may be seen in a hysteresis loop). Similarly if the current is 
made, an error occurs if the flux does not start from zero 
value. 

The expression for computing the flux is F = kRD/ N, where 
k is the constant of the galvanometer, R the resistance (external 
-fgalvanometer resistance), D the observed deflection, N the 
number of turns of the exploring coil. If the galvanometer is 
one with considerable damping, k will vary greatly with the 
resistance, being constant only at high resistances, and the 
curve or table giving the k values must be referred to. If only 
relative values of flux are required, for instance, the variation 
of flux with generator field current, no value of k need be 
obtained, the flux being proportional to RD, the product of 
resistance and deflection. 

In computing the flux it is necessary to note carefully 
whether, as is usually the case, the constant of the galvanometer 
is given for a reversed current, and whether the observations 
correspond. For instance, in calibrating, the current is usually 
reversed, and flux observations of a permanent magnet made 

31 



by withdrawing the coil must always be multiplied by two, if 
the ordinary k of the galvanometer is used. 

When observing quantitatively, see that the whole flux 
change occurs before the galvanometer coil has moved through 
any considerable portion of its swing. This is readily tested by 
waiting a fraction of the galvanometer period, perhaps a second 
or two, before pressing the key, after which there should be no 
deflection. 

The swing of the galvanometer coil is stopped either by 
short circuiting through a proper key, if the galvanometer is 
damped considerably, or by a counter torque obtained by 
applying in the proper direction a small fraction of the voltage of 
a cell through a suitable reversing key. 

The calibration of the ballistic galvanometer is usually 
accomplished by reversing the current in a long air solenoid 
with an exploring coil surrounding the middle. The flux at the 
middle of the solenoid is 4irnAI/10, where n is the number of 
turns of the solenoid per cm., A the area and / the current 
(in amperes). 

SPEED AND FREQUENCY 

The primary standard for speed is an accurate speed counter 
and a reliable chronometer. The Company's chronometer is 
checked by Washington time, as time record is made on the 
laboratory through a special wire, daily at noon. 

Secondary or Working Standard 

The Company's working standard is a liquid tachom- 
eter having a scale 36 inches long and graduated from 300 to 
1200 revolutions per minute. This tachometer is coupled to a 
small variable speed motor, to the other end of which is con- 
nected through a nest of gears the tachometer to be tested. By 
means of these gears the tachometer' under test can be run in 
either direction and at speeds which are multiples of the range 
of the standard. This working standard is checked weekly by 
the standard speed counter and a watch which has been com- 
pared with the chronometer. 

The working standard for the vibration frequency indicator 
is a current interrupter of the vibration type, operated by the 
working standard tachometer and motor. For the Thomson 
station type, a machine running at the required frequency, 
checked by a speed counter and watch, constitutes the working 
standard. 

Tachometers 

The Company has in use the following types of tachometers: 
Veeder Liquid, Schaeffer and Budenburg portable, Niagara 
portable, Dr. Horn portable, Hopkins' electric portable and 
Frahms vibration portable. 

All portable tachometers should be checked running in both 
directions, as it is frequently found that they differ somewhat in 
their calibration whether run clockwise or counter-clockwise. By 

32 



"clockwise" is meant clockwise rotation of the tachometer shaft 
looking at the spindle end. 

Tachometers like the S.&B., Niagara and Dr. Horn types 
when run continuously need oiling every 3 or 4 hours. The best 
grade of clock oil only should be used on them. This type, 
although it is apparently strong and compact, is nevertheless 
a delicate instrument and should be handled as carefully as any 
other measuring instrument. 

The Veeder liquid tachometer- is a centrifugal pump arranged 
to pump the liquid from a small reservoir into a glass tube, the 
height of the liquid in the tube rising or falling with the speed. 
This type of tachometer has a small plug that can be screwed 
into or out of the reservoir, changing the level of the liquid in 
the reservoir and tube by displacing some of the liquid in the 
reservoir and thereby adjusting the zero. In the later types of 
Veeder tachometers, the zero is the lower surface of the inverted 
cone at the foot of the glass tube in the reservoir. The meniscus 
of the liquid in the column should be level with the lower surface 
of this cone. The liquid used is grain alcohol slightly colored 
with red aniline dye. Wood alcohol should not be used as it 
corrodes the shaft, causing the bearings to leak. If the tachom- 
eter leaks, it should be returned to the Standardizing Labo- 
ratory to be repacked. 

The Hopkins electric tachometer consists of a small magneto 
which generates about 200 millivolts at full speed and is used 
with a portable millivoltmeter or, where permanently installed, 
with a station instrument. 

There are two kinds of vibration tachometers; one is tuned 
to respond to the vibration of the machine, due to the speed; 
the other is an electromagnetic type. The former, however, is 
not satisfactory where more than one machine is running, as the 
reeds respond to the vibration of a machine adjacent to the one 
being tested. The electromagnetic type can be used conveniently 
when an accurate speed measurement is required at some distance 
from the machine. Not more than the rated voltage should be 
applied, as excessive voltage will cause a burn out. 

Frequency and Speed Indicators 

G-E Type H frequency and speed indicators are of the switch- 
board type and are convenient for use on testing stands. The 
two instruments differ in the scale only, one being graduated to 
read frequency and the other the normal speed and a certain 
high and low percentage of the machine speed on which it is 
used. In using these instruments, adjustments for wave shape 
must be made by shifting the arms on the resistance box used 
with the instrument before beginning a test. This can be done by 
measuring the speed of the machine by means of a speed counter 
and watch, and moving the arms until the instrument reads 
correctly. Both of these types are iron clad (shielded) instru- 
ments, and, therefore, they are not affected by stray fields. 

Frahrri 's system vibration frequency indicators and Hartman 
and Kempf frequency indicators are similar to the electrically 

33 



operated vibration tachometers but are graduated to read fre- 
quency. They have a voltage range of from 250 to 50 volts and a 
frequency range of from 90 to 223^ cycles. In the former 
(Frahm) the voltage adjustment is made by means of four taps 
on the resistance ; the binding posts being marked +, 65, 100, 130, 
180 and 250. In the latter type (H and K) a, small button is 
provided on the end for cutting in or out resistance when the 
instrument is first connected to the circuit. This button should 
always be in the 250 volt position, and after connection has been 
made, the button should be turned until the right amount of 
resistance has been cut out to correspond to the voltage applied. 

These instruments possess important advantages over 
tachometers in that they may be located at the testing table so 
that the instrument readings may be observed and the speed 
controlled by one man. They can be read more accurately and 
are not influenced by the direction of rotation. They may also 
be used to read the speed of d-c. machines or machines which 
are under-excited. For this purpose a current interrupter is 
provided on the shaft of a centrifugal tachometer. This inter- 
rupter is provided with binding posts which must be connected 
in series with the frequency indicator and a 125 volt d-c. circuit. 
They are also provided with disks having several contact points. 
For a disk having four contact points the frequency indication 
would be the same as that of an eight pole alternator. 

It is not safe to use these frequency meters for measuring 
the speed of a machine under test when it is first started, since 
they cannot always distinguish between 20 cycles or 40 cycles 
in consequence of the fact that both a 20 cycle and a 40 cycle 
reed will vibrate at 20 or 40 cycles. The speed should be roughly 
set to that desired, by reading the tachometer dial, after which 
it can be exactly adjusted by the frequency meter. Due to the 
many advantages of these instruments they should be employed 
wherever possible, in place of the ordinary tachometer for 
testing work. 

WAVE SHAPES 

The term wave shape is used to denote the generator e.m.f. 
wave, at no load. The voltage from a potential transformer 
secondary is transmitted to the Standardizing Laboratory, 
where the oscillograph is connected in. As the oscillograph 
current is only about 0.2 ampere, the load on the potential trans- 
former is inconsiderable. 

Generator potential waves at various loads of unity or 
other power-factors are sometimes required. When a series of 
waves is taken, the oscillograph is brought near to the generator 
or apparatus under test, and is in charge of an operator from the 
Standardizing Laboratory. 

Current waves are taken with the oscillograph connected 
across a shunt (similarly to a millivoltmeter). The resistance 
of the shunt should be selected to give a shunt potential drop of 
at least 0.2 volt. A current transformer of suitable rating may 
be used with a small shunt in the secondary. 

34 



The flux distribution on generator or motor pole faces is 
determined by obtaining the potential wave of a narrow exploring 
coil, usually of only a few turns, on the armature. In d-c. 
generators or motors the wave of potential between commutator 
bars is sometimes taken. Where temporary slip rings are used 
duplicate brushes should be placed on each ring to avoid the 
effects of chattering. 

When two waves, or three waves, are required together, 
taken in their proper phase relation, such as the potential and 
exciting current waves of a transformer, they are recorded 
together by two elements or three elements in the oscillograph. 

The Oscillograph 

The oscillograph, on account of its short period (about 
1 6000 second) can be applied in a great variety of tests where 
a knowledge of rapidly varying currents or voltages is required. 

For the oscillograph a d-c. circuit of about 8 amperes is 
required to operate the arc, field, shutter, and film-driving 
motor: the source is usually the 125 volt shop circuit. 

The oscillograph current proper is small; about 0.2 ampere. 
For current curves a shunt potential drop of at least 0.2 volt is 
required, as the resistance in the oscillograph is 1 to 2 ohms. 
One, two or three oscillograph elements may be used, the instru- 
ment being regularly built as a three-element oscillograph. The 
insulation between the elements is sufficient to stand several 
times the ordinary 110 volts. 

The oscillograph indication is adapted to the voltage by 
adjustable resistance. 

Its use for wave shapes is considered in preceding paragraphs. 

For currents and voltages on opening or closing a circuit 
the oscillograph is placed near the point of operation so that 
the operation may be effected during the period of exposure of 
the oscillograph. Where the operation is in response to a signal 
it is usually not practicable to make the exposure much less 
than a second. If it is necessary to have the record to a larger 
time scale so that the film must be driven faster than 60 rev. 
per min. for a shorter exposure than a second, the operating 
mechanism and the oscillograph shutter are actuated by one 
operator, or are connected together either mechanically or 
electrically. In some tests the exposure can include more than 
one revolution of the film, that is, the record may go more than 
once along the film. In some cases the film revolves much more 
slowly, to give an exposed record of several seconds or even a 
minute or more. 

For short-circuit tests of alternators, three-phase, quarter- 
phase or single-phase, two oscillographs are usually used together, 
one on the armature, and one on the field. If the record ends 
before the transient is over, an auxiliary exposure is sometimes 
made a few seconds later to obtain the permanent short-circuit 
condition of the alternator. It is customary to connect a 
resistance load across the exciter in parallel to the generator 

35 



field. For three-phase short circuits, shunts are connected in, 
one in each phase, on the ground side of the switch. 

Where the duration is required, and is not otherwise given, 
as frequently occurs in d-c. tests, one oscillograph element can 
record on an alternating current timing wave of known fre- 
quency; for instance, the 40 cycle shop circuit. 

Visual inspection on the screen, sometimes with the help 
of a moving mirror, is made for adjustment to a suitable scale, 
where practicable, before the formal photographic record is 
taken. 

RESISTANCE MEASUREMENTS 

Unit Employed 

The unit employed is known as the "International Ohm." 
It is represented by the resistance offered to an unvarying 
electric current by a column of mercury at deg. C, 14.4521 
gm. in mass, of a uniform cross-sectional area, and 106.3 cm. 
in length. The cross-sectional area of this column is approx- 
imately 1 sq. millimeter. 

Primary Standard 

The Company's primary standards consist of two 1 ohm 
units of the Bureau of Standards form and two 1 ohm units of 
the Reichsanstalt form, which are compared with the Govern- 
ment Standards at Washington and certified to by the Bureau 
of Standards. These certificates give the temperature at which 
the units are correct and the temperature coefficient, if any; 
i.e., the correction factor to apply when the temperature of the 
unit differs from the standardizing temperature. 

The Company has also other units of the same forms varying 
in resistance from 0.0001 to 10,000 ohms which are used as 
standards in connection with the 1 ohm units. 

Working Standards 

These consist of several current carrying units of various 
current capacities and resistance values. They are frequently 
compared with the primary standards referred to and also 
with each other. 

CLASSES OF RESISTANCE MEASUREMENTS 

There are three general classes into which resistance measure- 
ments may be divided. These are "Medium," covering a 
range from 1 to 100,000 ohms; "Low," covering a range below 
5 ohms; and "High," covering a range above 50,000 ohms. It 
will be noted that the division line between the classes is not 
very definite, i.e., the several ranges overlap each other. 

Medium Resistance Measurements 

For the measurement of medium resistance the "Wheat- 
stone Bridge" and the "Slide Wire Bridge" are used. 

36 






WHEATSTONE BRIDGE 

Two types are in use, the "Post Office" pattern and the 
"Decade" type. Both operate on the same principle. In the 
''Post Office" type the resistances composing the rheostat are 
all connected in series and the reading is obtained by adding 
all the values of the plugs that are out when a balance is obtained. 
In the "Decade" type (also the dial type) only one plug is 
used for each decade, and the reading is obtained directly, by 
noting the values against the plugs that are in when a balance 
is obtained. It is, of course, understood that in both cases 
proper account must be taken of the ratios as plugged in the 
"arms" of the bridge. Also, in both cases, only one plug in 
each arm must be used and the values must be taken from the 
plugs that are in. The following remarks will apply to both 
types of bridge. 

Good Contacts 

All plugs and other contacts should be kept clean and 
bright. The plugs should be cleaned every time the bridge is 
used or, if in constant use, at least every day. This may be done 
by wiping them with a piece of soft cloth or waste applied with 
the finger. Never use emery cloth or polishing powder. The 
key contacts may be cleaned by putting a piece of heavy paper 
between them, pressing the key and pulling the paper out. 
If very much corroded, a piece of worn crocus (not emery) cloth 
may be used. 

It is essential that all plugs should be tight. It is not neces- 
sary to use much force, in fact this should not be done. The 
plug should be given a slight rotary motion, at the same time 
applying a gentle pressure. In removing the plugs, give them 
a rotary motion in the same direction as when they were inserted. 
The rotary motion should be in a clockwise direction, to prevent 
unscrewing the plug heads. 

Using Keys 

To operate the keys (if they are in proper condition) only a 
firm steady pressure is necessary. Pounding the keys must not 
be allowed, since it ruins them. This applies to all testing keys, 
as well as to bridge keys. 

Choice of Ratios 

In using the Wheatstone Bridge, it is best that the resistance 
in the arms and the resistance in each of the four bridge arms 
should be as nearly equal as possible, as this gives the most 
sensitive arrangement. 

Most bridges have a capacity of 1 to 9999 or 10,000 ohms 
in the rheostat, with ratios for multiplying or dividing the 
rheostat plugging by 1000. It is not advisable where other 
means are at hand to use the 1/1000 or 1000/1 ratios, except 
on a bridge of unusually accurate resistance adjustments, as 
the 1 ohm coils are not as accurate as those of greater resistance. 
Avoid using 1 ohm coils as far as possible. 

37 



Temperature Coefficient 

For ordinary bridge work in the factory and in general work 
(outside of the laboratory) the temperature coefficient of the 
bridge may be neglected, as it is too small to be appreciable 
within the limits of the work under consideration. The temper- 
ature coefficient of the material in test, however, must always 
be considered; if an allowance for it is necessary to secure the 
desired accuracy, it should be made. Apparent disagreement 
between different departments frequently arises which on investi- 
gation will often be found to be due to a disregard of the tem- 
perature coefficient of the material under test. 

Should it be necessary to make a temperature correction 
for the bridge, great care must be taken to measure the temper- 
ature of the bridge coils correctly. A thermometer placed in the 
bridge box often does not nearly indicate the correct temperature 
of the^ coils, especially if the surrounding temperature is rapidly 
changing. The bridge should be kept in a nearly constant 
temperature and the indications of the thermometer in the box 
should remain substantially constant for at least one hour, 
preferably for two or three hours. 

SLIDE WIRE BRIDGE 

This is a modification of the Wheatstone Bridge, the slide 
wire forming two arms of the bridge and corresponding to the 
ratio arms in the Wheatstone. 

Ohmmeter 

The so called "Sage" ohmmeter is essentially a slide wire 
bridge arranged for portable use where approximate values are 
sufficient. 

This instrument is useful for special jobs and is found very 
convenient, especially on outside work, i.e., where no fixed 
bridge is available, such as in a power station, car barns, etc. 
Its sensitiveness and consequently its degree of accuracy is 
largely dependent on the hearing of the observer and the con- 
dition of the dry cell batteries forming a part of the instrument 
and supplying the necessary current for making a measurement. 
A telephone receiver of the "watchcase" pattern is used on 
this bridge in place of a galvanometer to determine when balance 
is obtained. 

• Instructions already given regarding contacts and plugs 
apply. In addition the slide wire and "contact finger" should 
be given proper attention. The wire can be wiped off with the 
finger or a soft cloth when dirty. The contact finger may be 
cleaned with crocus cloth. 

Under no circumstances use any emery or crocus on the slide 
wire as this will ruin the bridge. The bridge should be tested 
before starting on an outside job, to see if it is in working order, 
as the batteries deteriorate even when standing idle. Never leave 
the bridge connected, as metallic dirt or conducting material 
sometimes collects in the plug holes which may short circuit 
and spoil the battery if the receiver switch is not in working 

38 



order, as occasionally happens. This switch should receive 
occasional attention. 

The so called Weston ohmmeter is a low range voltmeter 
with a scale graduated to read in ohms. It will give fairly 







5 H3 



w 
o 

< 

. CO 
bo h 

E Pi 

o 
(J 

to 

O 

§ 
Pi 
<5 



accurate results if the potential employed is constant and its 
value properly taken into account. The inverse ratio of de- 
flections of the instrument without and with the unknown 

39 



resistance connected in series is a measure of the resistance in 
ohms. It is further described under the section on " High Resist- 
ance by D-C. Voltmeter." 

The "Evershed" ohmmeter is a true ohmmeter, because the 
scale readings are directly given in ohms and are independent 
of the current or voltages used. This outfit is not to be discussed 
here as its use has not been adopted. It is a valuable device 
for certain purposes; for further information refer to the 
makers or agents. 

A comparison of the Evershed with the methods used in the 
Sage and Weston ohmmeters show why the latter two are not 
true ohmmeters. The Evershed apparatus is also used for high 
and insulation resistances. 

Low Resistance Measurements 

Under this heading are included the "Thomson Bridge," 
sometimes called "Double" Bridge, and the "Drop Method," 
using an ammeter and voltmeter or their equivalents. Fig. 
15 shows the wiring for a special application of the drop method. 
This is used where the outfit can be permanently installed and 
a special operator employed; therefore, further explanation will 
not be given here. 

THE THOMSON BRIDGE 

This is a modification of the Wheatstone Bridge and is 
suitable for use with low resistances, as its arrangement removes 
the objection to the former, viz., the resistance of connections 
and plugs. It is also a modification of the "Drop Method" 
discussed later, but the accuracy of the results is not directly 
dependent on the value of the current employed. As this device 
is in the nature of a permanent fixture and a special operator is 
generally employed for its use, further explanation is not con- 
sidered necessary. 

The instructions, already given, in reference to contacts, 
plugs, slide wire, etc., also apply here. If a slide wire bridge 
is not provided with a roller the contact must not be moved 
until it is released from the wire. Failure to observe this will 
soon ruin the wire, especially if it is of small diameter. 

DROP METHOD (DIRECT CURRENT) 

For this method current and potential measuring instruments 
of suitable ranges are required, simultaneous readings being 
taken on each; from these readings the resistance is calculated by 

E 
Ohm's Law (i?= — ). 

The Current Standard must be connected in series with the 
resistance to be measured, and, where practicable, a suitable 
adjustable resistance for controlling the current. The volt 
standard is connected across the resistance to be measured, so 
as to measure its potential drop. A non-inductive resistance 
may be connected in series with the voltmeter to alter its sen- 

40 



sitiveness if required. This resistance should have a current 
capacity equal to that of the voltmeter. 

The instruments should be so chosen that the deflections 
obtained are reasonably large, in order to reduce the error of 
observation as much as possible. The current used should be 
sufficient to give a good deflection on the ammeter. It must not, 
however, be great enough to heat the resistance under test 
and thereby change its resistance. This point is very important 
and frequently overlooked; the greater the temperature coeffi- 
cient of the material of the resistance the more important it 
becomes. If the current employed in making the measurement 
is not steady, two observers should take observations, one 
reading the ammeter and the other the voltmeter. Simul- 
taneous readings should be taken, each reading being repeated 
several times, the average reading being used to determine the 
final result. Neglect in considering the ratio of the resistance 
of the voltmeter used to that of the apparatus under test some- 
times introduces errors. If the ratio is large (2000 or more) the 



r y =/OOor/ 
/feac/zng onV=0. Svo/£ 




law of divided circuits can be neglected and the result obtained 
from Ohm's Law as previously stated. If the ratio is small, 
allowance must be made, since a part of the current is shunted 
through the voltmeter, which is also measured by the ammeter. 
To illustrate this point take the following example, as per 
Fig. 16: 

Bv Ohm's Law R v = ' —=0.005 ohms. Whereas 

100 amperes 
making the allowance for shunted current through V (where r v 
= 100 ohms) we get £* = 0.00500025 or 0.005 per cent, a differ- 
ence too small to consider for this class of work. This is found 
as follows: 

The current i v through V is equal to the drop across R x or 

-4 d V f S =0-005 amperes. Now i x = I-i v or 100-0.005 
r v 100 ohms 

E 0.5 
= 99.995. Since the value of R x is equal to " 7 " = qq~qq = 

= 0.00500025, the value as given above. Again supposing r v = l 
and following the same reasoning we get R x = 0.005025 or 0.5 
per cent, a difference which is too large to be neglected. 

41 



High Resistance Measurements 

Under this heading, "High Resistance D-C. Voltmeter," 
"Insulation Resistance Measuring Sets" and "Meggers" are 
considered. 

HIGH RESISTANCE D-C VOLTMETER 

A high resistance instrument (50,000 ohms or more) is gen- 
erally used for high resistance measurements. For lower 
resistances, lower voltages and a lower resistance voltmeter 
may be used. The Weston ohmmeter belongs to this class. 
In these cases on the voltmeter, the deflection is directly pro- 
portional to the current flowing through it, and inversely 
proportional to the resistance of the circuit with constant 
potential across it. 

A constant potential of about 500 volts is usually employed. 
This voltage reading is determined by connecting the terminals 
of the supply directly to the voltmeter. The resistance to be 
measured is then connected in series with the voltmeter and a 
second reading made and noted. The resistance X is then given 

by the formula ir^=^; Then R m + X = ^ 

where R m = resistance of the voltmeter used; D m the deflection 
of the voltmeter with resistance in series; V the voltage of the 
supply when taking reading D m , and X is the resistance sought. 

If the value of X is large relative to R m it is not generally 
necessary to subtract R m to get X, and this is not usually done. 

In making these measurements do not attempt to use a 
voltmeter which reads lower than the voltage of supply, as in 
case the resistance is omitted the instrument is likely to burn 
out. Do not try to get results by this method unless the supply 
is steady and constant or a second voltmeter is connected directly 
to the line all the time with a second observer for taking simul- 
taneous readings. When two instruments are used do not get 
their resistance values mixed; the resistance of the instrument 
reading the voltage is immaterial. 

A suitable reflecting galvanometer calibrated to read in volts 
may be used in place of the voltmeter. The method and cal- 
culations are the same as described above. 

INSULATION RESISTANCE TESTING SETS 

The principle of operation is similar to that of the d-c. 
voltmeter, a shunt box being added to increase the range of the 
galvanometer which is used in place of the voltmeter in the 
other method. 

The galvanometer constant K = and the re- 

10 X c 
re- 
sistance = 77- c where D = deflection of galvanometer when 

taking constant; D 2 when making observation; S = multi- 
plying factor for shunt; R = resistance in ohms in series when 
taking constant ; C and C 2 = number of cells used when taking 
constant and observation respectively. 

42 



Complete instructions are furnished with the portable outfit 
when sent out. The permanent outfits work on the same 
principle and are generally installed with other testing apparatus 
where a special operator is available. 

The following points should be mentioned. The various 
parts of the entire outfit, including the connecting wires (both 
internal and external), must be properly insulated from each 
other and from earth to prevent leakages. If this is not done, 
leakage currents may pass through the galvanometer and not 
through the resistance being measured, thus falsifying the 
results. 

If the resistance being measured lies between the earth and 
some conductor, as is the case with a lead covered cable, one 
side of the galvanometer should be connected directly to earth, 
taking precaution to insulate the rest of the circuit well. To 
form an earth, a bare wire may be used grounded to earth, to 
which one side of the galvanometer is connected. With this 
arrangement, if any leakage occurs, the leakage current is 
shunted by the galvanometer and does not affect the readings. 
Where possible, leakage should be eliminated, but reasonably 
correct results can be obtained by testing, changing over the 
connections and averaging the results. 

When making insulation measurements on cables installed 
underground, tests should be made for earth currents. To do 
this, disconnect the battery and short-circuit the terminals to 
which the battery was connected. Then, connect to ground and 
to line and observe the galvanometer deflection. If there is no 
deflection no earth currents exist, if there is a deflection of 
constant direction and amount a dead resistance equal to the 
internal resistance of the battery can be substituted in place of 
the short-circuiting wire and the amount and direction of the 
galvanometer deflection can again be observed. This deflection 
is added to or subtracted from the deflection obtained when 
making the test, before dividing into the constant. Since the 
battery resistance is small compared to the resistance under test, 
it can usually be neglected and the deflection used as obtained 
with the short-circuiting wire. If the earth currents are very 
appreciable or unsteady in amount or direction, the test should 
not be taken until the conditions are more suitable. 

Chloride of Silver Dry Cell Batteries are generally used to 
supply the current for these resistance measurements. 

These cells are very quickly ruined by short-circuiting or 
using them on too low a resistance. The cells should never have 
less than 5000 ohms per cell connected in series with the circuit 
connected to them. 

Never put into the battery covers wires or other material 
which could short-circuit the cells. The space between the 
covers and cell tops may seem to be a convenient place to 
carry spare wire but this practice causes trouble. Abrasion of 
the insulation on the lead wires supplied with the batteries may 
short-circuit the cells, and must be watched. 

43 



The cells should be tested before using to see that they are 
in good order (giving about 0.8 to 1 volt). In any case the e.m.fs. 
of the cells must be sufficient to allow the operator to get correct 
results. The resistance of the voltmeter used should be at least 
5000 ohms, or if several cells in series are tested at once, the 
voltmeter resistance in ohms must be at least 5000 times the 
number of cells tested in series. 

It frequently happens that some of the cells in a battery 
give only a fraction of their proper voltage; in such cases the 
voltage of each individual cell must be considered when making 
a test, and the total voltage must not be estimated merely from 
the number of cells in use, but actually measured. 

Wherever possible, cells below normal voltage should be 
rejected and replaced by new cells. 

The " Marcuson Portable Testing Battery" is used when 
an outfit is permanently installed. As this is a form of storage 
cell it will stand an appreciable amount of current as compared 
with the Chloride of Silver Dry Cell Battery. The voltage is 
also more dependable and being about twice as much per cell 
requires only half the number of cells. 

The galvanometer shunt boxes and series resistances are 
marked with different units from those used on the portable 
outfits and a slightly different formula is used but the principle 
and general arrangement are the same. As there is a special 
operator where more sets are installed, further mention will not 
be made here. 

MEGGER 

This instrument, developed by Sidney Evershed, of London, 
combines, in one convenient case, both the measuring instru- 
ments and the current supply apparatus. The current is fur- 
nished by a magneto generator operated by a hand crank. 
Those in use by this Company are known as "Constant Pres- 
sure Meggers," and the drive is through a slip device so that the 
proper speed is maintained after having once been reached. 
The proper speed can easily be determined after a few trials. 
It is only necessary to turn the crank fast enough, as the gener- 
ator cannot be driven at too high a speed. 

The insulation to be measured is connected between the 
two terminals, the crank turned, and the insulation resistance 
read directly from the scale while the crank is being operated. 
If one of the conductors surrounding the insulation is earth, 
this should be connected to the terminal on the megger marked 
"earth." 

Before a measurement is taken all leads should be discon- 
nected and the index set to "infinity." This is done by turning 
the crank and bringing the index to read "infinity" by operating 
the index adjuster. 

These instruments are made in several capacities ranging 
from 40 to 2000 megohms full scale deflection and should be 
selected according to the resistance to be measured. 

The magneto in these instruments generates a voltage as high 
as 1000 and a very uncomfortable shock may be received. Care 

44 



should therefore be used in handling the leads or touching the 
terminals when the magneto is in operation. 

The instrument is very conveniently portable and for outside 
work is generally to be preferred to the insulation resistance sets. 

MEASUREMENT OF ELECTROMOTIVE FORCE 

The unit of electromotive force is the international volt. 
This is the electrical pressure, which, when steadily applied to 
a conductor the resistance of which is one international ohm, 
will produce a current of one international ampere. Weston 
Standard Cells whose e.m.f. is certified to by the National 
Bureau of Standards are used as a primary standard of e.m.f. in 
the Standardizing Laboratory. 

The Potentiometer 

To compare an e.m.f. directly with the standard, the poten- 
tiometer is used. The e.m.f. of the standard cell is balanced 
against the drop of potential caused by passing current through 
the potentiometer shunt from a storage cell. This shunt consists 
of a series of adjusted resistance coils and a slide wire marked 
to scale. By setting the contacts of the circuit containing the 
galvanometer and the standard cell at scale points indicating the 
exact voltage of the standard cell, and adjusting the storage 
battery current until the circuit balances and the galvanometer 
reads zero, the potentiometer becomes direct reading. Any 
external d-c. voltage not exceeding 1.5 volts may then be read 
by balancing it against the drop across a suitable part of the 
potentiometer shunt. For extreme accuracy, a small correction 
is made to allow for known differences in the resistance of the 
various sections of the slide wire. To measure higher voltages 
a multiplier is used which will reduce 15, 150 or 750 volts to the 
1.5 volts required for the potentiometer. 

Voltmeters 

For a working standard of direct voltage a G-E laboratory 
standard d-c. voltmeter is used, and for alternating voltage 
a G-E laboratory standard a-c. voltmeter. These are frequently 
calibrated to the primary standard. In the case of the a-c. 
instrument, reversed readings are made in calibration, to insure 
agreement between the a-c. and d-c. calibrations. The instru- 
ments to be calibrated are compared with the working standards 
by means of a system of multipliers which give the necessary 
range to the working standard. 

For the measurement of direct voltages, G-E Type DP2 
D'Arsonval voltmeters are used. There are also a few Weston 
instruments still in use. These give a range from 1 to 750 volts 
with full scale reading, and, by means of multipliers, up to 3000 
volts. These instruments operate by the torque produced on a 
movable, current-carrying coil located in the field of a permanent 
magnet. A very powerful stray field may partially demagnetize 
or cross-magnetize the instrument and permanently change its 
calibration. The DP2 instruments are shielded; some of the 

45 



Weston instruments are not. The unshielded instruments are 
easily affected by stray fields. These instruments are also made 
up as millivoltmeters with low resistances, with low scale read- 
ings from 200 millivolts up. 

Never connect any instrument marked " Millivoltmeter " or 
"Special Meter" across higher voltage than it reads, otherwise 
the instrument will burn out. To measure voltage higher than 
the capacity of the instrument a multiplier may be placed in 
series with it. Then if E is the corrected reading of the volt- 
meter, V the voltage to be measured, R v and R m the resistances 
of the voltmeter and of the multiplier, 

V = EX Rv ~t Rm 

Rv 

or, two voltmeters may be placed in series and careful simul- 
taneous readings taken; the sum of the two corrected readings 
is the voltage to be measured. One of the two voltmeters may be 
considered as a multiplier for the other; then if E\ and £2 are the 
corrected readings on the two instruments at one point, and E 
is the corrected reading on the first instrument at any other 
point, 

For both a-c. and d-c. instruments the Standardizing Lab- 
oratory furnishes a curve and sometimes a certificate. On these 
curves the correction to be added to or subtracted from the 
instrument reading is plotted against the indication of the 
instrument. The certificate shows the comparison of the read- 
ings of the instrument with those of a correct standard. These 
curves and certificates should be used to correct readings and 
to determine the proper reading for any voltage required. 

The Laboratory also furnishes a constant, A~, for d-c. instru- 
ments which are used in the Testing Department. This con- 
stant K is such that if V = corrected voltage and E = reading of 
of the instrument, 

V = KXE 
V 
From this E =-^ 
A 

Therefore, to obtain the reading on the instrument which 
corresponds to the voltage required, divide the correct voltage 
by the constant of the instrument. Since these constants are 
never far from unity, the equation 

E = (2-K) X V= V+(l-K) X V 
is nearly true. This is the most convenient method for getting 
the proper reading. 

Illustration : 110 volts required, K = 1.003 
E=V + (l-K)XV 

= 110 + (1-1. 003) XI 10 
= 110-0.003X110 
= 109.67 

46 



This constant should be used only to make an approximate 
correction and should not be used where an accuracy of 0.5 per 
cent or better is desired. 

D-C. voltmeters should be disconnected from field circuits 
while the field switch is being opened, because of the inductive 
kick, which frequently bends the needle. They should also be dis- 
connected from synchronous motor or synchronous condenser 
fields, while the machines are starting from the a-c. side because 
of the high alternating voltage developed by transformer action 
in the field windings during starting. This voltage will some- 
times puncture or burn out a voltmeter. 

A voltmeter should always be connected through a double- 
pole switch, and should be kept out of circuit when not in use, 
as its readings may change with long continued heating. The 
cover glass should never be rubbed before reading on account of 
the electrostatic effect on the needle. If a cover glass shows 
electrification, it may be discharged by moistening it with the 
breath. No moisture should be allowed to reach the inside of 
the instrument. 

Two types of Thomson voltmeters are generally used for 
the measurement of alternating voltage, — Type P and Type P3. 
The P3 instrument may also be used on direct voltage without 
sensible error, but the P instrument must not be so used for 
accurate work unless nearly full scale readings are taken. These 
instruments have a range of from 15 to 750 volts full scale read- 
ing. 

On account of the spreading of certain parts of the scale, an 
a-c. voltmeter cannot be used with accuracy as low on the scale 
as a d-c. instrument. In general a P instrument should not 
be used below }/$ its maximum reading. The P instruments, 
containing no permanent magnets or shields, are also sensitive 
to the action of stray fields, especially if this field alternates at 
the same frequency as the voltage applied to the instrument. 
They should, therefore, be kept away from masses of iron and 
from cables carrying heavy currents, and should be placed at 
least two feet from other instruments. The P3 instruments 
are much less sensitive to stray fields, and may be placed within 
two inches of one another without sensible error. 

Cables carrying heavy currents, whether direct or alternating 
current, should be kept close together. They must never pass on 
opposite sides of a machine standing on an iron floor. If an instru- 
ment reads alike in four positions 90 deg. apart, it is unaffected 
by stray fields. Protection from stray fields for an unshielded 
instrument is sometimes obtained by placing the instrument 
in an open topped iron box. The accuracy of the indication, 
however, may be slightly changed by the proximity of the iron 
to the field of the instrument. 

Care should be taken that voltage leads are always connected 
to the points between which the difference of potential is to be 
read. Thus, in reading volts across the armature on a com- 
pound wound d-c. machine, the leads should be attached to the 
brushes, while in reading volts across the machine thev should 



be attached to the outer end of the series field and the brush 
ring of opposite polarity. In any circuit where voltage drop is 
measured, the resistance of an extra connection in the main 
current circuit included between the voltmeter contacts is often 
sufficient to cause serious error. Only the voltmeter current 
should flow through the voltmeter leads. 

Potential Transformers 

For most commercial alternating voltages a 130 or 150 volt 
voltmeter is used in connection with a potential transformer. 
The transformer voltages given in the following table are in 
common use. In addition to this list of standard transformers, 
there are in the Testing Department a few transformers of 
other descriptions for special uses. 

STANDARD POTENTIAL TRANSFORMER VOLTAGES 



Primary Volts Secondary Volts 


OIL INSULATED, IRON CASE 


13200 
11000 


110 
110 

■ 


DRY INSULATED, IRON CASE 




6600 
5500 


110 
110 


DRY INSULATED, MARBLE BASE 

» 



3300 

2200 

1100 

550 

220 



110 
110 
110 
110 
110 



DRY INSULATED, PORTABLE, WOODEN CASE 



1100/2200 
550/1100 



110/220 
110/220 



Most of these transformers are designed for use at any fre- 
quency from 25 to 60 cycles. They are tested with a load of a 
single instrument at from 80 to 120 volts secondary and should 
not be loaded with more than two instruments nor used outside 
this range of voltage or frequency except when special arrange- 
ments have been made with the Standardizing Laboratory and 

48 



the transformers have been checked under the proper conditions. 
The transformer primary must be connected to the line and the 
secondary to the instruments. 

In the portable type there are four primary and four second- 
ary terminals, from which three voltage ratios may be obtained; 
viz., series multiple, multiple multiple or multiple series con- 
nection. For series connection, the two inner terminals are 
connected and the lines or instrument leads are connected to the 
two outer terminals. For multiple connection, the two terminals 
on one side are connected to one line or lead and the two on the 
opposite side are connected to the other. The cases of the iron 
potential transformers should always be grounded. No changes 
should ever be made in connections with the high potential on. 

MEASUREMENT OF CURRENT 

The primary standard of current is the silver voltameter 
which is used for comparison occasionally. The practical 
standard used is a set of very accurate standard current-carrying 
resistances. The voltage drop across these resistances is meas- 
ured by the potentiometer. The current value is then obtained 
by multiplying the voltage by a constant depending on the 
resistance used. 

A G-E laboratory standard millivoltmeter used in connection 
with a multiplier and set of shunts constitutes the working 
standards of direct current. The working standards for alternat- 
ing current include a series of Kelvin balances covering a wide 
range of currents. ! The working standards are calibrated from 
the potentiometer, reversed readings being used for the balances. 
The portable instruments are compared with the working 
standards. 

For the measurement of direct current, G-E Type DP2 
ammeters and some Weston ammeters are used. The DP2 
instruments are self-contained with full-scale readings from 
150 milliamperes up to 30 amperes. The Weston instruments 
are self-contained up to 200 amperes. The DP2 millivoltmeters 
of 200 millivolts full scale are used with G-E portable shunts 
from 30 to 3000 amperes capacity. For higher ranges manganin 
oil-cooled shunts are used in connection with the same millivolt- 
meter. There are also some 500, 1000, and 2000 ampere shunts 
of 400 millivolts drop at rated current which are used in con- 
nection with 400 millivolt Weston instruments. For heat runs 
where high accuracy is not required, Thomson station shunts 
ranging up to 15,000 amperes are used with DP2 millivoltmeters 
of 60 millivolt full scale. This combination has an appreciable 
temperature coefficient, and should not be used for accurate 
measurements without special instructions from the Standard- 
izing Laboratory. 

In reading a millivoltmeter attached to a shunt, assume the 
end of the scale to represent the rated amperes of the shunt, and 
read the result accordingly. To correct for instrument error, 
multiply by the instrument constant, or use the certified values. 
In case the millivoltmeter and shunt have been certified as a 

49 



unit, the correction shown in the certificate includes errors of 
both instrument and shunt. If the instrument error is separately- 
certified, correction may be made for the shunt error by multiply- 
-p 

ing by -=r=, where E= rated volts drop of the shunt, / = rated 

current of the shunt, and R = actual resistance of the shunt. 

This correction is very small, and may usually be neglected. 

For measuring current beyond the capacities of the instru- 
ments at hand, two ammeters may be placed in multiple; but 
both instruments must be read simultaneously at every point. 
If two shunts are used in multiple, millivoltmeters must be con- 
nected to each and readings taken on both. 

For the measurement of alternating current, Types P and P3 
ammeters are used. The general statements as to voltmeters 
apply equally to ammeters of the same type. The ammeters are 
somewhat more likely to produce stray fields, especially the high 
current instruments. Ammeters should be protected by a short- 
circuiting switch, which is kept closed except when reading. 

The usual method of measuring high alternating currents is 
by using current transformers in connection with low reading 
ammeters. The standard commercial G-E transformers have 
a 5 ampere secondary. These are used in the Testing Depart- 
ment for all purposes. Current transformers have a core and 
windings like a low voltage, high current power transformer, but 
are insulated to stand considerable voltages, but they should 
never be used on circuits whose voltage exceeds that given on 
the nameplate. The ratio given by the Laboratory for a point 
is accurate at that point, but the ratio varies somewhat for lower 
or higher currents. The secondary should not carry more than 
two instruments. The secondary circuit of a current trans- 
former must never be open while current flows through the 
primary. If this precaution is not taken, there is danger of 
the transformer overheating and thereby breaking down the 
insulation. There is also danger to anyone handling the second- 
ary, owing to its high voltage. Opening the secondary while 
current flows in the primary also magnetizes the transformer 
core, which causes a change in the ratio of currents and in the 
phase angle between them. The transformer should, if subjected 
to this high magnetization, be carefully demagnetized before 
being relied on for precision work. 

Demagnetization may be carried out by putting at least one- 
half load primary current through the transformer with 10 ohms 
or more connected to the secondary, in series with the instru- 
ments to be used. This resistance should then be gradually 
reduced to zero, by steps of one ohm or less. All these trans- 
formers can be used on circuits operating at 25 to 125 cycles. 

To measure the currents in a three-phase circuit, two equally 
rated current transformers and three ammeters are necessary. 
The primaries of the two transformers are placed in two of the 
lines; the secondaries are connected with like polarities together 
(straight connection); a common connection is added so as to 
short-circuit both secondaries. One ammeter is placed in each 

50 



separate transformer secondary circuit; the third ammeter goes 
in the common line, and reads the current in the third phase. 
Where both voltage and current are small, as in the testing of 
small induction motors, three similar current transformers should 
be used to avoid unbalancing the circuit. 

MEASUREMENT OF POWER 

There is no primary standard of electrical power in practical 
use. Wattmeters for general use are tested on direct current; 
for special accuracy, particularly under low power conditions, 
alternating current is used for the test. In the d-c. test, 100 
volts, as given by a laboratory standard voltmeter is applied to 
the potential circuit of the wattmeter, and current, measured 
on a laboratory standard ammeter, is sent through the watt- 
meter current circuit. The product of the volts and amperes 
gives the true watts. Readings are taken direct and reversed 
and the average is used as the true a-c. value. When the a-c. 
test is made, the wattmeter is compared directly with a cali- 
brated dynamometer. If a test at low power-factor is desired, 
the phase position of the voltage supplied to the potential 
circuits of the instrument and the standard is controlled by a 
phase shifting transformer. 

P and P3 instruments are used in the Testing Dept. Their 
potential circuits are for 150 volts, with current circuits ranging 
from 1 to 200 amperes. The full scale readings range from 150 to 
20,000 watts. The P instruments are the more sensitive to stray 
fields. 

Never apply more than the rated voltage to the potential 
circuit. The current circuit will carry up to three times the 
rated amperes for a short time. The accuracy of the wattmeter 
depends but slightly on the ratio of current and potential 
applied. W T attmeter readings may be corrected by reference 
to curves or certificates as previously stated for voltmeters. 
Current and potential transformers may be used with wattmeters 
where the current or potential is larger than the wattmeter 
rating. The secondaries of current transformers used on poly- 
phase circuits with wattmeters should not be interconnected. 

When wattmeters are used with current or potential trans- 
formers, the potential circuit, current circuit, and case of the 
wattmeter should be connected together with a light fuse wire, 
to prevent differences of potential between the coils and case. 

If R w is the corrected reading of the wattmeter, C the certified 
ratio of the current transformer, and P the certified ratio of the 
potential transformer, 

True watts =PXCXRw 

When reading a small power at a moderately high voltage 
on a wattmeter, the wattmeter reading may be affected by the 
losses in the instrument itself. If the current flowing in the 
voltage circuit of the wattmeter passes also through the current 
coil, the wattmeter reads the losses in its potential coil. If a 
voltmeter is similarly connected, the wattmeter reads its losses 

51 



also. If E is the applied voltage and R the resistance of the loss 
circuit, then, since the circuit is practically non-inductive, 

loss=iT 

If the wattmeter and voltmeter are so connected as to 
prevent the current in the potential circuits from flowing through 
the current coil, the wattmeter reads the losses in its current 
coil, and the voltmeter reads the drop through the wattmeter 
current coil in addition to the voltage across the load. These 
errors are nearly always negligible. If the wattmeter reads the 
losses in potential circuits, a measure of the amount of the losses 
may be had by reading the wattmeter, after opening the load 
circuit so as to leave all instruments connected to the main 
lines. This is called reading stray power, and is a good check 
for leakage losses. 

In measuring the watts in a two-phase circuit, each phase 
should be considered as a separate single-phase circuit. The 
sum of the readings on two wattmeters gives the total watts. 

In a three-phase three-wire circuit two wattmeters should be 
used. The current coils should be placed in two of the phases 
and each potential coil connected from that phase in which its 
current circuit is placed, to the third phase. The algebraic sum 
of the wattmeter readings gives the total watts. The higher 
reading wattmeter is always positive; the lower reading is posi- 
tive if the power-factor is above 0.5, negative if it is below 0.5. 
To determine by test whether the reading is positive or negative, 
open the phase to which the wattmeter in question is not con- 
nected. This leaves a single-phase circuit on the wattmeter; 
if the wattmeter still reads forward, it will give positive values on 
the three-phase connection. If it reads backwards, it gives 
negative readings on three-phase. 

To read the watts in a three-phase four-wire circuit, three 
wattmeters should be used. The current coils should be con- 
nected in the three-phase lines, and each potential coil should 
be connected from the line in which its current coil is placed to 
the neutral line. The total watts equal the, sum of the corrected 
indications of the three wattmeters. The same method may be 
used on a three-phase three- wire system by connecting the 
potential circuit of the three instruments in Y, thus forming a 
neutral point for the instruments. The instruments must have 
equal resistances in the potential circuits. If potential trans- 
formers are used with the primaries connected in Y on a three- 
phase three-wire circuit, the secondaries should be connected 
in delta to the potential circuits of the wattmeters. 

If a wattmeter potential circuit is not absolutely non-inductive 
the current in it will have a slight phase displacement relative to 
the voltage across the wattmeter terminals. This is equivalent 
to a change in the phase angle between the voltage and current 
of the main circuit as read on the wattmeter. Hence, wattmeters 
are subject to an error, from which ammeters and voltmeters 
are free. If a current and a potential transformer are used 

52 



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54 



there is usually a further phase difference between primary and 
secondary current in the former, and between primary and 
secondary voltage in the latter. The result of these three 
angular changes is a change in the phase relation in the watt- 
meter. The total change rarely exceeds 2 degrees, and is fre- 
quently less than 30 minutes. At or near unity power-factor its 
effect on the reading is inappreciable; but at a very low power- 
factor large errors may result. 

Correction for Phase Angle 

Correction of wattmeter readings for errors due to phase 
angle of wattmeter, current transformers, and potential trans- 
formers, may be made as follows: — 

A — Single-phase circuits. 

(1) Correct all instruments for scale error. 

(2) Obtain a, the equivalent phase angle of the wattmeter, 
from the certificate. (This is very small for the P and P3 watt- 
meters, and can usually be neglected.) 

(3) Select £, the phase angle between the primary and 
(reversed) secondary currents of the current transformer, from 
the certificate, using the reading of the ammeter in series with 
the wattmeter. 

(4) Select 7, the phase angle between the primary and 
(reversed) secondary voltages of the potential transformer from 
the certificate, using the reading of the voltmeter in parallel 
with the wattmeter. 

(5) Determine cos 2 , the apparent power-factor from the 

readings of the ammeter, voltmeter and wattmeter (corrected 

according to Xo. 1) by the formula 

^ , . Watts 

Power-factor = — - w 

volts X amperes 

(6) Add algebraically a, /3 and 7, using the signs as given 
in the certificates. 

(7) Select the correction factor from Tables 1 or 2. In 
these tables a series of values of ( a-\-(5-\-y) is given in the left 
hand column; in the first line across the top of the columns is 
given a set of values of the apparent power-factor (cos 02-) 
The correction factor is found in the column under the proper 
apparent power-factor in line across the page from the proper 
value of ( a +0+7). For values lying between those given in the 
tables, interpolation will give sufficient accuracy for most cases. 

Table 1 should be used when ( a + +7) is a positive angle 
and the power-factor of the circuit supplying the wattmeter 
is lagging, or when ( a +/3 +7) is a negative angle and the power- 
factor of the circuit is leading. 

Table 2 should be used when ( a +/3 +7) is a positive angle 
and the power-factor is leading, or when ( a +/3 +7) is a negative 
angle and the power-factor is lagging. 

(8) True watts = wattmeter reading corrected according to 
(1) X certified ratio of current transformers X certified ratio of 
potential transformer X correction factor for phase angle. 

55 



If the greatest accuracy or values outside the limits of the 
table are required, the following method may be used: 

Follow (1), (2), (3), (4) and (5) as given herewith. If cos 6 
represents the true power-factor of the circuit, being considered 
a positive angle for lagging current and a negative angle for lead- 
ing current, 

0=02 + (a+/3+ 7 ) 
Then 

True watts = wattmeter reading corrected according to 
(1) X certified ratio of current transformer X certified ratio 

of potential transformer X — 

cos 6 2 

— is the correction factor given in Tables 1 and 2. 

Co$ 02 s 

B — Three-phase three-wire circuits with currents and voltages 
balanced. 

When two wattmeters or a polyphase wattmeter are used 
with similar current transformers whose secondaries are equally 
loaded and not interconnected the total watt reading may be 
corrected for phase angle by the same method as on single-phase, 
using the apparent power-factor of the three-phase circuit which 
is 

Total wattmeter reading 
3 X volts (delta) X amperes of one line 
instrument corrections being applied as per (1). 

C — Other polyphase circuits. 

On three-phase four-wire circuits, three-phase three-wire 
circuits, whose currents or voltages are unbalanced, and two- 
phase circuits each wattmeter should be treated as a separate 
single-phase instrument obtaining the apparent power-factor 
from its reading and of the voltmeter and ammeter in the same 
phase, consequently using a different correction factor for each 
wattmeter. On a three-phase three-wire circuit using the two- 
wattmeter method, it should be noted that the current is fre- 
quently leading in one wattmeter and lagging in the other. 

MEASUREMENT OF POWER-FACTOR 

Watts 



The power-factor of a single-phase circuit = . , 

b ^ volts X amps. 

It is usually obtained by using the readings of the voltmeter, 
ammeter and wattmeter. 

In a balanced three-phase circuit, the power-factor may be 
obtained from the two wattmeter readings. If a is the phase 
angle, the power-factor = cos a, and R is the ratio of the smaller 
to the greater wattmeter reading, 

Tana=—~y/3 

56 



The principle of the General Electric Company balanced 
three-phase power-factor meter uses this fact. The elements 
are so combined into one instrument that the position of the 
pointer depends on the ratio of the watts. The instrument is 
quite accurate, and independent of frequency. 

The volt-amperes in a balanced three-phase circuit are 
equal to the product of the amperes per line, the volts between 
lines, and the square root of three. 



57 



CHAPTER 3 

ASSEMBLY OF MACHINES FOR TEST 

HANDLING MATERIAL 

When erecting large apparatus for test, methods of handling 
and transportation are of prime importance. Each piece of 
apparatus must of course be handled with reference to its 
special construction. Practically all of the handling of the larger 
machines and parts is done by the crane men and crane followers, 
but each test man should become familiar with the correct 
methods of handling such material and see that such work is 
carried on in the approved manner. 

There is a great difference between ropes and slings used for 
hoisting. In ropes the wear can always be seen by the strands 
becoming frayed, loose, or cut. A chain, except for a few 
bruises, will not show any signs of weakness, even though, at 
the same time, it may be full of small cracks which cannot be 
seen by the naked eye, or it may be much crystallized by long use. 

Care should be used in every case to see that satisfactory 
slings and ropes are used to lift apparatus. 

There are many varieties of hitches and knots, some of 
which are shown on the following pages. 

Wire cable slings occupy a very important place in hoisting 
and have been found very satisfactory when carefully used. 

In using slings of any kind care should be taken to see that 
one section does not lie on top of another and thus put an undue 
strain on the outer section. 

It often happens when a rope sling is used double that the 
ends of the rope are passed through the double part. Unless this 
is done carefully the effect of only one part will be obtained 
instead of two. 

Increased Stresses Due to Angle of Slings 

When a weight is lifted by two or more slings connected to 
the crane hook and making an angle with each other, the increase 
in the stress of the individual slings must be considered. On 
account of this angle between the two sets of slings the stresses 
on each set is greater than half the total load, and increases very 
rapidly as the angle between the sling and the work is decreased. 
An angle of 45 degrees between the sling and the work makes 
the stress in each sling % of the total weight, and the collapsing 
force between the two points of attachment to the work is equal 
to Yi the weight. This collapsing force acts in a direct line 
between the two points of attachment. If the work is ring 
shaped, it would tend to deform the ring. A spreader of suffi- 
cient stiffness should be used between these two points to resist 
this collapsing force. It will be seen that eyebolts are not 
suitable for attaching the slings to the work unless a spreader 
is used to relieve them of this side pull, which would put a 
heavy bending moment on the shank of the bolt. 

58 



Reducing the angle between the sling and the work to 30 
degrees makes the stress in each sling equal to the total weight 
and the collapsing force is also equal to the total weight. Such 
a small angle should never be used if avoidable. 

The following tables show how the safe load becomes very 
much smaller when the slings are used at an angle instead of a 
straight pull. 

SAFE LOAD IN LB. ON MANILA ROPES AND SLINGS 





Two Part Sl/ng 


Two Part Sling 


Two Port Sling 


Two Port Si in g 


Rope 


i 


i 


A 






Diam. 






/ \ 


y/\ 




in In. 






/ \ 


/ \ 


^^\^ 




Vertical Looc/ 


60° Angle 


45"Ang/e 


xn"Angle> 


V?. 


500 


435 


355 


250 


% 


1000 


870 


710 


500 


Vx 


1500 


1300 


1065 


750 


V* 


2000 


1750 


1420 


1000 


1 


3000 


2600 


2125 


1500 


IK 


4000 


3475 


2830 


2000 


IV? 


5000 


4340 


3540 


2500 


1U 


8000 


6940 


5665 


4000 


2 


10000 


8680 


7080 


5000 


2H 


13000 


11285 


9200 


6500 


2V 2 


16000 


14880 


11325 


8000 



SAFE LOAD IN LB. ON WIRE CABLE OR SLINGS 





Two Port Sling 


Two Part Sling 


Two Part Sling 


Two Port Sling 


Wire 


i 


i 


A 






Cable 
Diam. 
in In. 






A 


/\ 


/^ 




Vertical Load 


60 "Angle 


45°Angre 


30°Angle 


V?, 


4000 


3470 


2830 


2000 


% 


6500 


5625 


4590 


3250 


u 


9000 


7800 


6350 


4500 


Vh 


12000 


10400 


8500 


6000 


1 


16000 


13870 


1 1300 


8000 


IK 


24000 


20800 


17000 


12000 


iy 2 


38000 


32900 


26900 


19000 


w 


50000 


43300 


35300 


25000 


2 


64000 


55500 


45250 


32000 



59 



SAFE LOADS FOR EYEBOLTS 

When it is necessary to use eyebolts for lifting loads no 
greater strain should be allowed than given in the table on 
page 61, which gives the safe load in pounds up to and including 
bolts 2 3^ in. in diameter. 

It should be understood that to obtain the greatest strength 
from an eyebolt, it must fit reasonably tight in the hole into which 
it is screwed, and the pull applied in a line with the axis of the 
screw. 

Eyebolts should never be used if considered the least faulty. 
They should never be painted when used for miscellaneous 
lifting, as paint is very apt to cover up flaws. They should be 
tested occasionally by tapping gently with a hammer but not 
sufficient to bend or to otherwise injure them. If it does not 
impart a good ring one of two things is the reason. It may fit 
too loosely in the hole, or there may be a flaw. 

Where a bolt is to be used for anything like its maximum 
load it should be screwed in tight with a bar and given a gentle 
tap with a bar or hammer to see if it imparts a solid feeling. 
If not, it should not be used. 

The strains set up in an eyebolt when used at an angle 
are very severe, due to the bending action of the bolt, and it 
is very liable to break where it is screwed into the work. This 
is shown very clearly by the table on page 61, that gives the safe 
load when used for a direct pull, and also shows how the strength 
of the bolt rapidly decreases according to the angle that may 
be used. 

SAFE LOAD ON ROPES AND CHAINS 

The tables on page 62 give the safe loads which may be put 
on manila rope, wire cables, and chains. The first column gives 
the diameter of the rope or chain, the second column gives the 
safe load which the rope or chain is to carry singly. In a sling 
where the strain is carried by two ropes or chains, the load 
given in third column should be used. In a sling where four 
parts of the rope or chain carry the load, the figures in the fourth 
column should be used. Figures are in tons of 2000 lb. each. 

The figures given in the above table are for cases in which 
the slings are in constant use and subjected to ordinary shop 
practice. Where cables of known high tensile strength are used 
these figures may be increased proportionately. 

The loads for manila rope should be used only when the rope 
is in fairly good condition; when badly chafed or worn the load 
should be reduced in proportion. 

As there are a great many different kinds of material to handle 
in the various parts of the Works, and in order to familiarize 
those engaged in the actual handling of these materials, a short 
table of the weights of the various materials is given on page 62. 

The weights of cast iron, steel, copper and lead are given 
in pounds per cubic foot. The weights of wood, concrete, stone, 
earth, brick, mortar and marble are also given in pounds per 
cubic foot. 

The weight of shafts is given per lineal foot. 

60 




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61 





SAFE LOAD IN 


TONS, VERTICAL LOAD 




MANILA ROPE 


WIRE CABLE 


CHAINS 


Dia. 
of 


Safe Load 
in Tons 


Dia. 

of 

Rope 

in In. 


Safe Load 
in Tons 


Dia. 

of. 

Chain 

in In. 


Safe Load 
in Tons 


Rope 
in In. 


Single 


Two 'Four 


Single Two 


Four 


Single 


Two Four 


Rope 


Part Part 


Rope 


Part 


Part 


Chain 


Part i Part 


V2 


H 


h\ a 


y 2 


1 


2 


y 


y 


% 


iy 


b A 


% 


A: % 


% 


m 


SH 


sy 


% 


i 


m 


3 


% 


% 


%\ Wa 


%. 


2y 


±y 


9 


y 


2 


sy\ e 


H 


A 


1 i 2 


% 


sy 


6 


12 


% 


3 


5 1 9 


1 


Va 


iy 2 \ 2y 2 


i 


4 


8 


16 


Va 


5 


9 15 


lfc 


1 


2 3 


IX 


6 


12 


24 


y 


6 


IOH'18 


\y. 


IX 


2H\ 4 


\y, 


10 


19 


36 


i 


8 


14 24 


1% 


2 


4 6 


i% 


13 


25 


48 


iy 


11 


19 


33 


2 


2X 


5 8 


2 


16 


32 


60 


iy 


13 


23 


39 


2U 


SA 


6^11 










iy 


18 


32 


54 


zy 2 


±A 


8 13 



















WEIGHTS OF VARIOUS MATERIALS 



Material 



Weight per 
Cu. Ft. in Lb. 



Weight per 
Cu. In. in Lb. 



METALS 



Cast iron 
Steel 
Copper 
Lead 



450 
489 
552 
709 



0.26 
0.28 
0.32 
0.41 



WOOD 



Ash 
Pine 



45 
38 



MISCELLANEOUS 



Concrete 

Stone 

Earth 

Brick 

Mortar 

Marble 



155 
180 
72 to 110 
100 to 150 
100 
180 



SHAFTING 



Diameter 
in In. 

6 

8 
10 
12 
14 
16 



Weight of Shafting in Lb. 
per Lineal Ft. 

95 
169 
264 
368 
517 
676 



62 



Approved Methods of Handling 

Fig. 17 to 39 show some of the approved methods of 
handling apparatus in the factory. 



iSL 



__* 



Fig. 17 
TWO CRANE EQUALIZER 

Used with two cranes of different lifting capacities, when 
lifting a load of greater weight than the safe capacity of one 
crane. For example: in the case of a weight of 90 tons, which 
is to be lifted by two cranes; one having a capacity of 60 tons, 
and the other a capacity of 30 tons. The hooks of the equalizer 
should be located so as to bring the center of the weight one- 
third of the length of the beams away from the end attached to 
the 60 ton crane. This arrangement brings two-thirds of the 
weight on the 60 ton crane and one-third of the weight on the 
30 ton crane. 




i 



Fig. 18 
ONE CRANE EQUALIZER 

63 




Fig. 19 
BLACKWALL HITCH 



Exceedingly useful where material is to be drawn along the 
floor, or for hauling cars on a level, or where the hitch is to be 
made quickly, or where a change is frequently required. 



64 



xvvs 




Fig. 20 
CLOVE OR DOUBLE HALF HITCH (METHOD;OF.MAKING) 




Fig. 21 
CLOVE OR DOUBLE HALF HITCH 

Very useful in the hands of a trained rigger, but, except for 
hauling, should not be generally used where other slings are 
available. 

65 




Fig. 22 
BOWLINE KNOT 

First position necessary in making a bowline knot. 




Fig. 23 
BOWLINE KNOT 



Second position necessary in making a bowline knot. 




Fig. 24 
BOWLINE KNOT 

Third position and completed bowline knot. If properly 
made this knot cannot slip. 

66 




Fig. 25 
BOWLINE ON A BIGHT 

The "bight" of a rope is that part which is doubled. There 
should be very little occasion for using this knot outside of the 
riggers' department. 



67 




Fig. 26 
SQUARE OR REEF KNOT 



slip. 



Used only for joining two ropes together. This knot cannot 



68 




Fig. 27 
STUDDING SAIL HITCH 

May be used very properly for hoisting timber or such 
material. 




Fig. 28 
SHEET BEND IN EYE 

Generally used for an adjustable sling. It can be adjusted 
quickly, and is a safe and useful sling in the hands of trained 
riggers. 

69 




Fig. 29 
TIMBER HITCH 



Used principally for hoisting rough lumber. 




Fig. 30 
TIMBER AND HALF HITCH 

Very useful for hoisting shafts or timbers in a vertical 
position. 



70 




Fig. 31 
SPLICED ROPE SLING 




Fig. 32 
LIFTING BLOCKS 



A method of protecting the cable on sharp corners is by 
means of the corner blocks shown. 



71 



Fig.133 
WIRE CABLE SLING 



Proper way of using in connection with a hook. 




Fig. 34 
LIFTING REVOLVING FIELD 



Two or more double slings should be used, depending upon 
the weight, the slings to be placed behind two adjacent arms 
and protected by means of padding. 



73 




Fig. 35 

PROPER WAY TO LIFT AND TURN REVOLVING FIELD 

(FIRST POSITION) 

A double set of slings should be used on the main hoist to 
lift the field high enough for turning; padding being used wher- 
ever necessary to protect the slings from sharp corners. 



74 




Fig. 36 

PROPER WAY TO LIFT AND TURN REVOLVING FIELD 

(SECOND POSITION) 

The field having been hoisted high enough for turning, a 
piece of timber or scantling should be placed through the bore 
of the field, the other end of the scantling to be connected to the 
"small hoist" by the sling; then by lifting on the "small hoist" 
and lowering on the "main hoist" the work is turned over. 
Great care should be used, especially against chafing or cutting 
of the slings. 



75 




Fig. 37 
LIFTING MOTOR-GENERATOR SETS 




Fig. 38 
LIFTING A BASE WITH STANDARDS 

Frequently a base and standard are lifted and no provision 
is made for any lateral strains that may occur; tending to place 
an unnecessary strain on the bolts fastening the standards to the 
base. When such a lift is to be made a piece of timber should be 
placed between the bearings to relieve the strain, as shown. 

77 




Fig. 39 
METHOD OF LIFTING ARMATURE TO ASSEMBLE 
IN BEARINGS 



78 



ERECTING MACHINES FOR TEST 

Blocking — General Remarks 

The cast iron bases, blocks, rails, etc., used for temporary 
foundations for machines in test are called "blocking." 

In setting up a self-contained machine, that is, one with its 
own base, shaft and bearings, the only blocking necessary is that 
required to allow the stator to clear the floor and it should be 
placed so that the bearings and frame are well supported. 

The blocking, in all cases, should be as low as possible and 
the necessary height should be obtained with the least number 
of sections. Many machines come to test without base, shaft 
or bearings, and the test blocking must be arranged to meet such 
conditions. 

All blocking must be securely clamped or bolted in place, 
the latter method being preferable. The height of blocking 
necessary is found by measuring the distance from the supporting 
foot to the bottom of the stator. If the machine has a base, 
the thickness of the base should be subtracted from this measure- 
ment. 

Shafts 

All self-contained machines are tested on their own shafts. 
The assembling of the shaft in the rotor will be discussed later. 

Machines without base, shaft or bearings require the use 
of a temporary or shop shaft and bushings of the right size to 
fit the shaft and the bore of the rotor. 

Shop shafts should be frequently tested in a lathe to be sure 
that all parts of the shaft run true. The bushings should also 
be carefully inspected to see that they are free from burrs and 
are not worn either on the inside or outside. In assembling 
shafts in rotors care must be taken to see that the shaft and bore 
are clean and free from burrs. 

Lubricate the shaft and bore thoroughly with a mixture of 
white lead and lard oil. 

If bushings are to be used, slip one bushing on the shaft and 
introduce the shaft into the rotor and slip the other bushing 
into the other end of the rotor hub. 

When bushings are used on a shop shaft the rotor is held in 
position by a collar on each side of the hub. Where a shaft is 
used without bushings there will be pressure enough obtained 
to hold the rotor in position without the use of collars. The 
collars should not obstruct the air passages of the armature. 

In pressing shafts into the rotors of self-contained machines 
great care must be exercised to see that the rotor is located on 
the shaft in the exact position called for on the drawing, other- 
wise the end play will be defective. 

The most accurate method of locating the rotor on the shaft 
is as follows: 

From the shaft drawing lay off the distance on the shaft 
from the center of a journal to the center line of the rotor; 
measure back from this point the distance from the center line 

79 



of the rotor to the back end of the hub. When the rotor is in the 
correct position on the shaft the end of the hub will be at this 
point. 

In measuring from the center of the rotor to the end of the 
hub several different points on the circumference of the punch- 
ings should be taken, as owing to the unevenness of the punch- 
ings one distance might be a little greater or less than the 
average distance, and the average distance is the one that should 
be used. 

The shaft is usually started into the bore with a heavy ram 
swung from the crane, a piece of heavy fiber being held between 
the end of the shaft and the ram to prevent injury to the shaft. 
The shaft is then placed in the hydraulic press and forced in. 
As soon as the rotor reaches the correct point on the shaft the 
power must instantly be released. 

The pressure usually required between shaft and bore is 
five (5) tons per inch of diameter of shaft on horizontal machines. 
A pressure of four (4) tons per inch will pass, but below this 
amount the pressure obtained should be reported to the proper 
superintendent who will decide whether it will pass. 

The bore is usually scraped to a standard pin gauge and the 
allowance for pressure is made on the shaft. 

Bushings 

Bushings one-half (%) inch or less in thickness are usually 
made of steel. The thicker ones are made of cast iron. 

In order that the bushings may go on the shaft and into the 
bore without excessive ramming which would soon destroy them, 
they are bored from 0.001 to 0.003 in. larger, and turned from 
0.001 to 0.003 in. smaller than standard. 

This will make a comparatively loose fit between the shaft 
and rotor and the rotor must be held in position by some form 
of clamp or set-screw collar. 

This looseness though immaterial on most large machines 
is sometimes troublesome on small ones, especially small high 
speed direct current machines as it may cause unbalancing, or 
it may cause the commutator to run eccentric and thus cause 
poor commutation. For this reason, a shaft without bushings 
should be used whenever it is possible. 

Couplings 

Shop couplings are required to be driven on and off shafts 
easily; they therefore do not have a very tight fit and so must be 
held in place with a set-screw the same as used with a pulley. 

Whenever a flange coupling is put on a shaft it should be 
faced off either in a lathe or in its own bearings to insure that the 
face runs in a plane perpendicular to the center line of the shaft. 
The set screw should be tightened before facing the coupling. 

If a coupling has been faced off and then removed from the 
shaft it will probably run out of true when it is re-assembled 
on the shaft, so it is better to test a coupling every time it is 
assembled on a shaft. In facing off a coupling on a shaft in a 

80 



lathe it is of the greatest importance to see that the journals 
run true when the shaft is turning on center because when the 
shaft is in its bearings it is the journals that determine how the 
coupling runs and not the lathe centers. 

In connecting two shafts with a flange coupling the face of 
each half of the coupling must revolve in a plane perpendicular 
to the center line of the shaft and the center line of one shaft 
must be a continuation of the center line of the other. 

The first condition is assured by facing off the couplings as 
described above, and the second condition is obtained in various 
ways. 

For example, the bearings in which the shafts turn may be 
located and aligned by stretching a fine wire between the centers 
of the two outboard bearings and adjusting the position of the 
other bearings to this line. In this case, allowance must be 
made for the natural sag of the line, which depends on the length 
and tightness of the line. For tables of sag and method of 
using steel wire for aligning shafts, see article by A. H. Nourse 
in the American Machinist of March 5th, 1908. 

The usual method of aligning two shafts with flange couplings 
is to bring one coupling up to the face of the other and as nearly 
into the correct position as can be judged by the eye, and then 
to move the pillow block by a bar or jack until the faces of the 
couplings are exactly parallel to each other. This condition can 
be determined by gauging the distance between the faces. If 
a gauge can just be inserted in the space between the coupling 
at several different points, the faces are parallel. The height can 
be adjusted very readily as it is usual to have the couplings made 
with a projecting ring on the face of one half and a corresponding 
recess in the face of the other one. Care should be taken to see 
that the coupling bolts are a good fit in the holes, otherwise each 
bolt may not be equally stressed and some bolts may shear off. 

Several designs of flexible couplings exist; but two types 
are much used in the works. One coupling consists of two parts 
of four arms each, the arms of one part interlocking with those 
of the other. These arms are separated by rubber buffers. The 
other type has its two parts laced together by a leather belt. 

In flexibly connecting two shafts the shafts need not be 
exactly in line, although they should be so adjusted as closely as 
possible, without spending too much time on the alignment. 

Assembly 

Apparatus delivered from the Manufacturing Department 
can be divided into two general classes, viz., self-contained 
machines which are delivered completely assembled; and 
machines which may or may not be self-contained, but which are 
delivered to test partially or wholly dismantled. It is usually 
the practice to align and center in the machine shop before 
delivery to test, all machines having their own bases, whether 
they are delivered completely assembled or not. It is, therefore, 
important to consider the precautions and methods which have 
been found necessary in assembling apparatus for test. 

81 



Cast iron bases, especially those used in connection with 
medium size and large apparatus, do not possess the necessary 
stiffness to allow them to be erected without proper support 
on the iron floor or testing blocks. Care must, therefore, be 
taken when setting machines in the testing stand to see that 
there are no chips, or lumps, under the blocking or base which 
may spring the base or destroy the alignment. It is well to 
measure the distance between pillow blocks after the base and 
lower half of frames are in place (in the case of split frame 
machines), before the rotating parts are placed in the bearings. 

All reference marks or assembly marks (usually numbers) 
on machines, except on those of the vertical type, will be found 
at the right hand side of the machine when facing the com- 
mutator or connection end. When the machine, therefore, is 
properly assembled, all marks should appear on that side. 

Before placing the shaft in its bearings, the surface of bear- 
ings and journals should be well oiled. After the shaft carrying 
the rotating parts has been assembled, a measurement should 
be made of the air gap. If the air gap is not uniform, or does 
not agree with the drawings of the machine, the trouble must 
be rectified. The gap can be equalized on top and bottom by 
inserting shims under the frame feet. If the gap does not 
equalize laterally it is usually corrected by shifting the frame 
and redoweling the frame feet to the base. 

Air Gap 

The measurement of air gaps is important on all apparatus. 
Air gaps on direct current machines are measured in the follow- 
ing manner: With the armature stationary, the gap should be 
measured at both the commutator and pulley ends, the measuring 
scale being inserted under each pole tip, without including the 
chamfer of the tip. A mark should then be placed on the 
armature circumference under the center of a given pole and the 
armature revolved through one pole span. The air gap measure- 
ment should be taken at the new position at the commutator 
end and so on for successive poles. The first set of measure- 
ments is known as the "stationary gap"; the second set as the 
"revolving gap." 

An eccentricity test of the armature is made by marking 
a point on one pole piece and measuring the air gap between 
this point and several equally space points around the surface 
of the armature punchings. These readings at once show if 
the armature will run true. If the armature will not run true 
the matter should immediately be reported to the office. 

On commutating pole machines the air gap measurement is 
taken under the center of the commutating pole. It is also 
necessary to measure the distance between the tip of each com- 
mutating pole and the adjacent tip of the main pole. The 
maximum allowable variation in this measurement is p- in. 
Should this amount be exceeded the matter should be referred 
to the office for instructions before proceeding with the test. 

Air gap measurements are taken on alternating current 
machines with the revolving field stationary, and also by 

82 



revolving it in a similar manner to that given above for "station- 
ary " and "revolving gap" on direct current machines, except 
that the air gap measurement on a-c. machines is taken at 
the center of the pole piece both on the front and back ends. 
In measuring the "revolving gap" it is not necessary to take 
the air gap measurement under each pole. The measurement 
need only be taken at points spaced 45 mechanical degrees 
apart. That is, eight (8) sets of measurements are required 
for the "revolving gap." 

The average gap as taken must check with the requirements 
as given on the Engineering Instructions. Fifteen (15) per cent 
variation is allowed between the maximum and minimum read- 
ings when measured from iron to iron and 20 per cent variation 
is allowed when measured over the binding wire. On machines 
using shims the average gap must be as close to Engineering 
instructions as can be obtained with a 14 mil shim. 

vSince the air gaps of induction motors are small, and since 
a uniform gap is important, they are measured by special 
gauges provided for that purpose. In using these gauges they 
are passed completely through the motor air gap from end to 
end of the punching. This gap measurement is taken at sev- 
eral points about the circumference of the rotor with it station- 
ary and revolving in a similar manner to that indicated above. 

Testing instructions which are issued from the office, in 
the case of special machines, give the length of air gap required 
for a particular machine, hence, the length of air gap measured 
should be checked against this information. If discrepancies 
exist, the matter should be immediately referred for instruc- 
tions, before starting the machine for test. When air gap 
measurements are made, a critical inspection should be made 
of the clearance between the rotor and windings or other parts, 
to insure that it is sufficient to allow the machine to operate 
without any surfaces striking or rubbing together. This may 
occur if the windings project unnecessarily and in no case must 
clearances be so small as to be unsafe. Should such cases 
occur, the trouble must be corrected and the proper clearances 
obtained before the machine is started for test. 

Air gap measurements should be made from iron to iron 
whenever possible and never from the wooden wedges of the 
armature. 

Brushes 

In preparing commutating machines for test, the brushes 
must be equally spaced around the commutator, 180 electrical 
degrees apart. The brushes on a stud must align properly 
with each other, and with the commutator bar from the front 
to the back end of the commutator. To space the brushes 
place a strip of paper tape around the commutator and mark 
the paper where the ends overlap. Remove the paper tape 
and divide it with a scale, or dividers, into as many equal divi- 
sions as there are poles on the machine. Then replace the paper 
around the commutator and paste the overlapping ends to- 

83 



gether. Space the brushes by the marks on the paper, taking 
care that the holders are clamped to the stud in the proper 
position. 

In some cases brushes are run trailing and in others leading, 
with reference to the direction of rotation. Radial brushes 
are also sometimes used. 

When the brushes have been set, fit them to the commutator 
surface. To do this, use a strip of sandpaper between the corn- 




Fig. 40 
RADIAL, LEADING AND TRAILING BRUSHES 



mutator and brush face. Coarse sandpaper is used first to 
obtain an approximate fit. Follow with very fine sandpaper. 
A close and accurate fit with the commutator is essential to get 
good commutation tests. When sandpapering, the sandpaper 
must be held close to the commutator to prevent rounding the 
tip of the brush when drawing the sandpaper away. The sand- 
paper should be drawn in the direction of rotation. These 
instructions apply also to fitting carbon brushes on collector 
rings. When the sandpapering of the brushes is finished, the 
resulting carbon dust must be blown from the armature or 
rotating part. The air blast should be directed away from the 
rotating part, so that the carbon dust is carried completely 
away and cannot drift into the windings. The leading, trailing, 
and radial brush setting is shown in Fig. 40. 

84 



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O /O eo 30 40 SO GO 70 30 £>0 /00 
Pressure /6s. £><?/- sg.//?. J Droj.&/'ea 

Fig. 41 

OIL RING BEARING, STILL AIR, ROOM 

TEMPERATURE 25° CENT. 



SO 




/O 20 30 40 ^O 60 70 0O &0 /OO 
/^r&sst/re /£>. pe/~s<z-//7 prv/\ area 
Fig. 42 
OIL RING BEARING, WELL VENTILATED 
ROOM TEMPERATURE 25° CENT. 

85 



In case copper gauze brushes are used a form and file, or 
emery paper, must be used to fit them to the commutator 
or collector ring. Copper brushes are now seldom used on com- 
mutators. Copper leaf brushes, as used on synchronous con- 
verters, are so constructed that no special fitting is required. 
They must, however, be properly adjusted in the holder to make 
good contact upon the slip ring. 
Bearing Lubrication 

When oil-ring lubrication is used, the lubricating oil must 
not be allowed to get so low in the oil well that the ring does 

'§ 280 

^ 240 



200 

\/60 



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N £V0 400 £0O dOO /OOO0PO /600 2000 

Rubbing Speed in feet per minute 

Fig. 43 
SAFE MAXIMUM PRESSURE ON BEARINGS FOR EACH SPEED 

not dip into it. If this instruction is observed satisfactory 
lubrication will be obtained for all ordinary bearing pressures 
and rubbing speeds. For high bearing pressures, or high speeds, 
some form of forced lubrication is used. The oil is forced into 
the bearing either on the bottom, or the lower quarter and 
enters the bearing at a point such that the revolving shaft 
draws the oil under the shaft. Oil from forced lubricated bear- 
ings is usually returned to an external cooling tank, where 
its temperature is reduced before being again pumped into 
the bearing. Oil rings and forced lubrication are occasionally 
used on the same bearings, so that if the oil pressure fails the 
rings supply enough oil to prevent danger, until the oil pres- 
sure can be restored. 

A properly designed bearing may run hot from the following 
causes: Oil rings sticking; scarcity or poor quality of lubricating 
oil; excessive local pressure in the bearing; insufficient relief 
on the sides of the bearings; improper alignment and exces- 
sive belt pull, or current flowing from frame to shaft. 

The remedy for the greater part of these troubles is obvious. 
In the case of excessive local pressure in the bearing, or insuffi- 

86 



cient relief on the side of the bearing, the remedy is to remove 
the high spots on the babbitt or bearing metal with a scraper 
and increase the side clearance. 

Allowable bearing pressures, speeds, etc., are given in Figs. 
41, 42 and 43. 

Before starting a machine all bearings must be filled with 
the proper amount of oil. Bearings should be inspected to 
see the}* have not been carelessly filled, viz., that oil has not 
been spilled on the bearing housing, or bearing shell, or upon 
other parts associated with the bearing, otherwise, a false 
impression may be obtained as to oil leakage or throwing when 
under test. To give the bearing a critical test for oil leaking 




Fig. 44 
TYPES OF OIL GAUGES 

or throwing, the dividing line between cap and bearing pedestal 
and between bearing brackets, should be painted with whit- 
ing. The end of the commutator or field spider adjacent 
to the bearing should also be given a white coating, so that 
it is possible to detect, after a comparatively short run, the 
slightest leakage or throwing of oil. 

Bearings with the end of the bearing shell visible should 
be filled with oil until it touches the lower part of the shell 
at the end of the bearing housing. Where the end of the bearing 
shell cannot be seen the bearing should be filled to within Y% in. of 
the top of the visible portion of the oil gauge glass; in the case 
of sight gauges to within 3^8 in. of the top of the gauge. In the 
case of overflow gauges having no glass, a record of the distance 
of the oil level from the top of the gauge must be made, in 
every case, upon the Testing Record. Gauges with glass tubes 
so placed as to show the oil level (Fig. 44a) are used on bearings 
of large machines, and stand pipe gauges (Fig. 44b) on small 
and medium size machines. Overflow gauges (Fig. 44c) are 
those with the top of the stand pipe fitted with a hinged cap. 

Oil gauges on most induction motors are of the overflow 
type, and should be filled to within tV in. of the overflow. As 

87 



already stated, no oil must be spilled upon the bearing parts. 
In filling bearings a funnel must be used and the oil inserted 
through the sight holes for the oil rings, or through the opening 
above the shaft at the end of the bearing housing. 

During test no oil should be allowed to leak or be thrown 
from the bearings upon the rotating parts, or windings. This 
is especially true with reference to commutating machines, 
where it is important that lubricating oil be kept away from 
the commutator, brushes and fittings. Should oil-leaking or 
throwing on these parts be detected during the test, the test 
should immediately be discontinued and the cause of leakage 
removed. If bearings under test rise in temperature 40 degrees 
cent, or more, above the room temperature, it should be reported 
to the office as a defect, since no properly designed bearing 
should heat above 40 degrees rise under normal conditions. It 
will usually be found that a greater temperature rise is due to 
a faulty bearing. 

Thrust Bearings 

There are two classes of thrust bearings; those which depend 
upon a film of oil between two flat plates, and those which have 
either hardened rollers or balls rolling between two hardened 
surfaces. The first class may be sub-divided into (a) those 
which are supplied with oil under pressure and (b) those which 
revolve in a bath of oil. In both these classes the bottom plate 
is stationary and the top one rotates with the shaft. 

In the pressure thrust bearing the two plates are recessed 
for about half their diameter and the remaining annular ring is 
scraped or ground to a true surface. Scraping is perhaps pref- 
erable to grinding as in a ground plate there is a possibility of 
particles of the abrasive becoming imbedded in the surfaces and 
causing them to cut. The bottom plate usually rests upon a 
spherical surface which allows the plates to align themselves 
in their proper relative positions. The oil is led from the pump 
or accumulator to the recess between the plates and the pressure 
raised until the plates separate and the oil passes out between 
the plates and up along the shaft to the overflow where it escapes 
and returns to the pump or cooling tank. 

It is obvious that the pressure per sq. in. required to separate 
the plates is a function of the superincumbent weight and the 
area of the bearing plates. The limit of allowable pressure per 
sq. in. on this type of bearing is the capacity of the pumps or 
accumulator, as the friction is purely fluid friction and the plates 
do not come in contact with each other. If an accumulator is 
not used it is necessary to interpose between the pump and the 
thrust bearing some form of baffler which will cause a back 
pressure on the pump above that required to separate the plates 
of the thrust bearing. This difference in pressure between the 
two sides of the baffler should be from 25 to 40 per cent of the 
pressure required to lift the plates. For example; if it requires 
1000 lb. per sq. in. to separate the plates, the pump should show 
a pressure of from 1250 to 1400 lb. per sq. in._ This insures a 
uniform flow of oil through the plates, which condition is 

88 



absolutely necessary for correct operation of this class of thrust 
bearing. 

The amount of oil which should be passed through a pressure 
thrust bearing varies with the diameter of the plates and this 
amount in gallons should be about 100 per cent of the diam- 
eter of the plates in inches. Thus a 20 inch thrust bearing 
requires about 20 gallons per minute. 

In operating this kind of a thrust bearing some reserve 
source of oil pressure, such as a spare pump, should be at hand 
in case of the failure of the one in service. Both pumps should 
be on the line constantly and each pump should be capable of 
supplying the necessary amount of oil to the bearing. If one 
pump fails the other can carry the load while repairs are being 
made. A check valve should be placed in the line from each 
pump so that the oil cannot escape if a valve or some other 
vital part of the other pump should fail. 

The other style of plate bearing revolves in a bath of oil and 
is grooved in such a way that the top plate draws a film of oil 
between itself and the bottom plate. 

A type of thrust bearing of this kind is a segment bearing. 
The novel feature of this bearing is a series of adjustable surfaces 
mating with a continuous thrust collar. The parts carrying these 
adjustable surfaces are referred to as "shoes" or "segments" 
and are free to adjust themselves, thus bringing about uniform 
distribution of load over the entire bearing surface and, further, 
and more important, adjust themselves at a slight angle with 
the collar and thus glide or skim over the oil film which adheres 
to it. 

The "shoes" consist of heavy steel blocks faced with babbitt, 
their upper faces forming the adjustable bearing surfaces. 
Each "shoe" fits into a recess in the body casting and is mounted 
on a spherical topped block in contact with another spherical 
topped block below, which provide the adjustment to running 
conditions. 

Below each shoe seat is an adjustable wedge for raising and 
lowering to bring about a uniform distribution of load. 

Machines equipped with bearings of this type require a con- 
siderable amount of power to start, consequently, they are 
usually assembled in the Testing Department with a pressure 
step bearing underneath them so that they may be easily 
started. The "step-block" is then lowered until the machine 
is supported from the upper thrust bearing. 

Unusual care should be exercised in first starting bearings 
of this type and the machine should be brought to speed very 
slowly to be very certain that the bearing is operating properly. 

ROLLER BEARINGS 

The roller type of thrust bearing (see Fig. 45) consists of 
several hardened steel rollers held in a brass retainer and arranged 
radially to the shaft. The rollers revolve between hardened 
and ground steel plates, one of which is stationary and the other 
revolving with the shaft. In this form of bearing the oil is not 

' 89 



under pressure but must be supplied quite liberally. The oil 
must enter as close to the shaft as possible so that the centrifugal 
force may throw the oil out across the surface of the disks. 
Rapid starting of a new roller bearing often causes trouble by 
scoring or drawing the temper because the hardened steel plates 
as they come from the grinder are not in proper condition for a 
bearing surface. This trouble can be avoided by lapping the 
plates or by running several hours at slow speeds thus giving the 
plates a chance to smooth themselves. The amount of oil that 
should pass through a bearing of this type is very indefinite. 




Fig. 45 
VERTICAL ROLLER THRUST BEARING 

The sole function of the oil is to keep the bearing cool and just 
what this amount may be for a particular bearing is hard to 
predict but will probably be from 10 to 14 gallons per minute 
on bearings up to 30 in. diameter. In any special case it is better 
to be guided by the advice obtained direct from the manu- 
facturers of the roller bearing in question. 

Roller bearings have been made as large as six feet across the 
disks and carry 2,500,000 lb. 

Balance of Rotating Parts 

Static Balance 

Rotating parts are usually balanced by putting them on 
a shaft and laying the shaft on two parallel rails called balance 
ways. The balance ways must be carefully leveled and well 
supported to prevent deflection from the weight of the piece 
to be balanced. After the correct amount of balance weight has 
been determined, a suitably formed weight is made and securely 

90 



fastened to the inside of the rim, or at a point at the same 
distance from the center as that at which the temporary weights 
were supported. The weights should be so fastened that they 
will not produce a shearing stress on the bolt or other fastening 
holding them in place. In revolving fields the weight should 
be placed on the inside of the rim. In this case the bolt has 
only to keep the weight from falling out when the machine is 
at rest. 

On d-c. armatures, pockets are generally provided into 
which melted lead is poured and hammered into place. 

On slow speed machines it is not necessary to get accurate 
balance, especially on heavy fields. On a 2000 or 3000 kw. 
field running about 120 rev. per min. an unbalanced weight of 
50 lb. would probably not be noticed. Vertical machines must be 
more accurately balanced than horizontal ones. 
Dynamic Balance 

A field with good static balance will not necessarily be in 
good balance when running. It is often necessary to rebalance 
a rotor dynamically after the machine is assembled. 

The shaft must be straight before any balancing is done. 
This can be determined by holding a pointer or pencil to the 
shaft and revolving the shaft slowly. If the pointer touches all 
points, the shaft is straight and the work of balancing may 
proceed. If it does not touch all around, the shaft is sprung 
and must be straightened before the rotor is balanced. On 
very heavy rotors it is not possible to balance them statically 
as a whole, because their weight will press the shaft sufficiently 
into the ways to prevent the rotor from taking its natural 
position. In this case the parts are balanced separately as 
carefully as possible and the whole is afterwards dynamically 
balanced, if necessary. 

To locate roughly the position proper for balancing, hold a 
pencil or chalk so that the high side of the shaft strikes it as 
the shaft revolves at normal speed. On a rigid shaft this mark 
will indicate the heavy side, but on a flexible shaft it will prob- 
ably show the light side of the rotating part. Put some weight 
on the side opposite the mark and try again. If the balance is 
better, the weight is in the proper place and the mark will 
be found to extend further around the shaft. If the balance 
is worse, the weight is on the wrong side. If the mark is found 
to have moved, weight should be added at the new point. If 
the mark is found on just the opposite side, too much weight has 
been added. 
Pulleys 

Pulleys are made of various materials such as cast iron, steel, 
steel rims with cast iron centers, wood rims with cast iron 
centers, paper rims with cast iron centers, etc. Paper pulleys 
are in common use, especially in the smaller sizes and when 
not subjected to dampness, they are preferable to cast iron or 
steel on account of their higher coefficient of friction. Steel 
pulleys have the advantage over cast iron in that they will 
stand a higher speed, are much lighter and are not liable to 

91 



have hidden cracks or flaws. A pulley should be made with 
a bore of such size that it will go on the shaft without pressure 
and should be held in place with set screws. All pulleys, especially 
cast iron ones, should be rigidly inspected frequently for cracks 
or other flaws. A speed of 5000 ft. per min. produces a tensile 
stress of about 1200 lb. per sq. in., which is the usual working 
stress allowed for cast iron pulleys. There are men detailed 
in the Testing Department whose business it is to inspect all 
pulleys after they are put on machines and again before machines 
are started. The practice of having pulleys inspected each time 
before a machine is started, must be rigidly adhered to. It is very 
essential that the shaft extend clear through the hub of the 
pulley. This will give the pulley a maximum working strength 
and will insure its not coming off the machine while it is running. 
The set screws in these pulleys must be inspected to see that they 
are in good condition, that the threads are not damaged, and 
that they extend through the hub to the key in the shaft. 

Flange pulleys are cast iron pulleys with a steel center. These 
are readily adapted to any machine by first fitting a coupling 
to the shaft and then bolting this flange pulley to the coupling. 
New centers are readily obtained for these pulleys so that they 
may be easily kept in first class condition. It is good practice 
to operate pulleys between 4000 and 5000 ft. per min. When 
not in use, they must be placed in the store-house provided for 
that purpose. 

Belts 

Leather belts are much used in the Testing Department and 
a considerable amount of power is transmitted by them. In 
no case, however, should a belt carry more than 400 kw. When- 
ever possible, endless belts must be used, as they are stronger 
and do not cause fluctuations in the electrical instruments as 
do laced belts. Laced belts must be examined very carefully 
before starting a test to see that the lacings are in first class 
condition, and all belts must be inspected before being used to 
see that they are riveted properly and in no way defective. The 
size of belt to be used must be carefully calculated by the Head 
of Section, and in no case should it be left to the judgment of 
the shop men. The belts must never be wider than the pulley, 
nor be allowed to run with one end overlapping the edge of the 
pulley, as this will surely injure the belts. They should be run 
with the tight side on the bottom if possible, and must be kept 
free from oil as this reduces the capacity very much and causes 
slipping on the pulley. Quarter turns in belts must be avoided 
if possible as this stretches the belts on one side and greatly 
reduces their capacity. Under no conditions is a belt to be 
overloaded; if it breaks it may seriously damage apparatus or 
injure men working in the vicinity. Belts, must, therefore, be 
regarded as sources of danger and possible accident. When not in 
use they must be returned to the store-house where they will be 
inspected and repaired by a man employed for that purpose. 

Whenever belts are running near an aisle, or passage way, 
guards must be so placed that men cannot fall, be thrown, or 

92 



drawn into them. The testing tables should never be set in a line 
with a running belt and work should be so arranged that an 
employee must not work continuously in line with belts, unless 
proper mechanical guards are provided. Whenever a belt is found 
defective, it must be returned to the repair shop for repairs. 



HP KM 



3e/t /6 20 24 28 32 36 
W/'dth -2oly- 3p/y 




44 48 32 36 60 64 68 72 76 80 inches 
4-p/y 4« 3p/y ~ 



Fig. 46 
WIDTH OF LEATHER BELTS 



Fig. 46 and the data on page 94 show the carrying capacity 
of leather belts of various widths and thicknesses "when running 
at speeds of from 1000 to 5000 ft. per minute. It is not per- 
missible to operate a belt in the Testing Department at a higher 
velocity than 5500 ft. per minute. 

When a belt is started for the first time it must be very 
carefully watched to see that it runs properly on the pulley, 

93 



and has the proper tension. Under no circumstances must an 
employee lean against, sit or stand upon, or pass through a 
belt even though it is not running. It is equally important 
that neither tools, nor articles of any description be laid upon 
belts after they are placed on the pulleys. 

DATA IN CONNECTION WITH WIDTH OF LEATHER BELTS 

The curves in Fig. 46 have been plotted from the following 
data: 

Coefficient of friction =0.4. 

Arc of contact = 165°. 

Weight of leather belting = 56 lb. per cubic foot. 

Centrifugal force =0.012 F 2 (with velocity in ft. per second.) 

7\ = 1. T 2 =0.316. 



Ratio tight over slack side=-^- 

■L 2 



3.1643. 



Torque or pull = Ti- T 2 =0.684. 
Greatest tension = T x +0.012 F 2 . 
Average thickness per ply = tf in- 
Working tension per sq. in. =275 lb. for laced belting. 
H.p. or kw. per inch in width of f% in. thick. 



1.05 

1.56 

2.03 

2.46 

2.855 

3.18 

3.447 

3.63 

3.73 



.783 
1.163 
1.514 
1.835 
2.129 
2.372 
2.57 
2.71 
2.78 



Width of Belt 

Up to 6 in. 
6 in. to 20 in. 
20 in. to 40 in. 
40 in. to 60 in. 
60 in. to 80 in. 



Up to 2 in. 

2 in. to 5 in. 

5 in. to 10 in. 
10 in. to 36 in. 
Above 36 in. 



Up to 2 in. 

2 in. to 5 in. 

5 in. to 10 in. 
10 in. to 24 in. 
24 in. to 36 in. 
Above 36 in. 



for 1000 ft. per minute, 
for 1500 ft. per minute, 
for 2000 ft. per minute, 
for 2500 ft. per minute, 
for 3000 ft. per minute, 
for 3500 ft. per minute, 
for 4000 ft. per minute, 
for 4500 ft. per minute, 
for 5000 ft. per minute. 

Curves Plotted with the Following Thickness 

1 ply belting varying from ^ in. to •& in. 

2 ply belting varying from ^ in. to ^f in. 

3 ply belting varying from -jjf in. to f| in. 

4 ply belting varying from f| in. to §J in. 

5 ply belting varying from f£ in. to l-^- in. 

Belts are to be Used in the Following Widths 

varying by \i in. 
varying by Yi in. 
varying by 1 in. 
varying by 2 in. 
varying by 4 in. 

Pulley Face to Exceed Width of Belt 

+ h 

+ y 2 
+ ^ 



74 

+ 1 

+iy 2 

+ 2 



94 



Before starting a test, the man responsible for the test must 
see that no one is in contact with the belt, and that nothing 
has been left lying upon it or where it may fall into it, while 
running. 

Truing Commutators 

The condition of a commutator determines to a great extent 
the satisfactory operation of the unit in service. A true periphery 
and a perfectly smooth surface are two requisites to satisfactory 
service. 

To secure these conditions is the aim of all commutator 
truing devices. There are two methods now recognized for 
truing commutators, viz., a turning tool and slide rest, sup- 
plemented by sandpaper, or some form of commutator grinder. 

In turning commutators some sort of a slide rest with a tool 
holder must be provided. In the Testing Department there 
are several sizes built on the same general plan, but differing 
principally in the length. The slide rest is held rigidly in such 
a position that the point of the tool is about on a level with the 
center of the commutator and movable parallel to the surface 
thereof. A very sharp diamond-point tool and a fine feed 
should be used. The cutting speed should be about 350 ft. per 
min. The end play must be eliminated by some means, usually 
by tying a board in such a position that it holds the armature 
securely against one oil deflector. After the commutator has 
been trued up as carefully as possible with the tool the final 
finish is obtained with either sandpaper or carborundum paper. 
Emery in any form should never be used because of the metallic 
particles which it contains. 

The objection to turning commutators is: first, that the cutting 
tool breaks the mica instead of cutting it; second, because of 
the different densities in mica and copper, the tool does not give 
a perfectly uniform surface and leaves the commutator bars 
a little higher in the center than on the edges; third, it is neces- 
sary to take a deep cut with the tool to get the required "bite" 
for cutting; fourth, the tool must be supplemented with sand- 
paper; fifth, the tool wears rapidly and must be replaced by 
another or re-ground during the process of turning. This is 
especially true when turning a commutator when the machine 
is run as a motor. When a tool is replaced in the middle of a cut 
it is difficult to prevent a score or a slight ridge being left where 
the new cut begins which can be removed only by taking another 
cut off the whole length of the commutator. This results in 
great waste of copper and decreases the life of the commutator. 
In truing a grooved commutator, that is, one from which the 
side mica has been cut out, it is very difficult to keep from carry- 
ing the copper across the slots when using a turning tool. This, 
of course, would necessitate cutting out the bridges of copper 
which on a commutator of any size means a considerable loss of 
time. 

The other, and perhaps the better method of truing com- 
mutators is with a commutator grinder. This consists essentially 

95 



of a small motor geared to a spindle which carries an abrasive 
wheel, the whole being carried on a slide rest similar to that used 
in turning commutators. The advantages of a commutator 
grinder over a turning tool are many; there is only one dis- 
advantage. The commutator can be ground with the machine 
running at normal speed and carrying full voltage. The grinder 
does not have to be so rigidly supported as the turning tool, 
and there is no danger of gouging the commutator as is the case 
with a turning tool. Grooved commutators can be ground with 
practically no bridging of the copper between bars. A com- 
mutator grinder can be installed, and the commutator ground 
without shutting down the machine. The commutator grinder 
produces an absolutely true surface from the fact that the 
grinding is done when the armature is running at normal speed. 
It is often the case that a commutator which runs true at slow 
speed will run eccentric at normal speed. 

Another important feature of the commutator grinder 
is the arrangement for catching all the copper dust. This 
consists essentially of a hood enclosing the grinding wheel 
leaving just enough opening for the wheel to come in contact 
with the commutator. A discharge pipe fitted with an ejector 
using compressed air produces a vacuum sufficient to draw all 
the chips away from the wheel and deposit them in a bag which 
is fastened to the end of the suction pipe. 

The disadvantage of a grinder is that it cannot remove 
copper as rapidly as a turning tool, and if the commutator has 
been allowed to become deeply grooved by the wear of the 
brushes, time would perhaps be saved by turning it, rather than 
grinding it. On the other hand, if the commutator is given the 
attention due it and attended to before the grooves become of 
appreciable depth, it will not only be better for the commutator 
to be ground, but it will prevent the necessity of removing a 
large amount of copper as would have to be done if the com- 
mutator were turned. 

Correcting End Play 

If a machine is properly leveled the rotor will revolve without 
rubbing either oil deflector when there is no field on the machine. 
If this is found to be the case, but that when field is put on the 
rotor pulls either one way or the other, it shows that the magnetic 
center of the field and armature do not lie in the same plane. 
This may be caused by the rotor being out of place on the shaft, 
or by the stator being out of its proper position on the base. 
It is evident that the defective end play may be corrected by 
moving either the rotor or frame. Whichever is found wrong 
should be made right, although perhaps it might be cheaper 
to move the stator than the rotor. 

The stators of the larger machines are not doweled till after 
the machines have been set up and tried out for both air gap 
and end play. 

If the machine were being installed outside where there were 
no facilities for pressing the shaft in or out of the rotor, the best 

96 



and certainly the cheapest way of correcting end play would 
be to move the frame on the base and redowel. 

If there is not sufficient clearance between the frame holding- 
down bolts and the holes in the feet, the holding-down bolts 
could have the body turned down as far as the depth of the 
thread, the reduced part being made of a length about Y± in. 
greater than the thickness of the foot and measured from the 
under side of the head. This will allow a much greater move- 
ment of the stator and w^ill not weaken the bolt if it is not 
reduced below the root of the thread. This method of correcting 
end play is sometimes used in the Testing Department, but 
after test the defect is always remedied by the shop, so that the 
proper position of the stator may be obtained without the use 
of the reduced bolts. 



97 



CHAPTER 4 

PREPARATION OF APPARATUS FOR TEST ; 
INSPECTION; WIRING; OBSERVA- 
TIONS DURING OPERATION 

Preliminary Inspection 

It is the aim to have all apparatus delivered to the Testing 
Department from the manufacturing department in a completed 
condition including fittings and all other parts. 

When apparatus is delivered, the man in whose charge it 
has been placed should make a very careful inspection for 
mechanical defects and should see that all parts as assembled 
check with the Testing Instructions. 

The following are some defects which may appear: Copper 
bridges formed between the bars over the side mica of the com- 
mutator, due to improper turning; bent end conductor or com- 
mutator leads; improper brush staggering; damaged insulation 
of armature and field spools; broken insulating boards on 
fields; insufficient clearance between bare electrical terminals or 
conductors and ground; poor joints between electrical conductors; 
loose terminals; bus rings or other connections improperly sup- 
ported; brush pigtails too long or touching the armature risers; 
too little clearance between a brush stud or various parts of 
fittings and ground; incorrect spring pressure; defective spacing 
of collector ring taps; defective spacing of lubricating brushes, 
etc. It should be noted that laminated pole tips are not bent 
and that cast pole tips are of approximately uniform thickness 
on all the main poles of the machine. All oil rings in each bearing 
should be visible through the bearing cap oil cover and the 
bearings should be properly filled with oil as described on page 
87. See that the brushes on collector rings ride properly on 
the rings and do not overlap. 

In fact a test man should place himself in the position of 
the customer and if anything about the machine does not 
appear right he should report it to the Head of Section. 

It is the duty of the Head and Assistant Heads also to look 
over the apparatus, but the man in charge of the machine will 
be held directly responsible. The Head or Assistant Head of 
Section must place the brushes of d-c. machines on the mechanical 
neutral and sign the Testing Record to that effect. 

The above inspection should also be made on all machines 
upon which changes have been made by the shop to make sure 
that no foreign material has lodged in the machine. 

Wiring 

Though a great deal of the wiring in testing work is tempo- 
rary, it must always be done as neatly as possible, due regard 
being paid to safety. All circuits should be protected by signs 
or barriers, where there is danger of any one coming in contact 

98 



with them. Conspicuously lettered danger signs are used to 
indicate the nature of the circuit. In addition to this, white 
tape is used around cables or apparatus carrying high voltages. 
After a tester has completed the wiring of a machine, he should 
notify the Head of Section, or Assistant Head of Section, to 
inspect the same. The Head of Section, or Assistant Head of 
Section, must then assure himself that it is satisfactory, and 
if so, enter his approval upon the Testing Record sheet and 
sign his name. 

The following general rules should always be followed in 
wiring apparatus for test. First, procure the print of connec- 
tions, which will be furnished by the Head of Section. 
The apparatus must then be connected up in accordance there- 
with. A copy of this print is sent to the customer with the 
apparatus, to help him in its installation. 

Checking the wiring during test serves the double purpose 
of detecting errors in the print, or wrong connections in the 
apparatus. It is consequently of considerable importance. 

In wiring apparatus for test, all the wiring should be com- 
pleted before any of the circuits are connected to the source 
of power, to prevent the necessity of handling live circuits 
while wiring. Where possible, one hand only should be used 
for connecting or disconnecting low voltage live circuits 
where an intervening switch cannot be used for making final 
connections. It must always be remembered that any circuit 
may become grounded and that some circuits are permanently 
grounded. The 125, 250, and 500 volt direct current shop 
circuits are permanently grounded. Hence, in all cases, circuit 
breakers must be wired on the positive side of the "125 volt" 
and "500 volt shop" circuits. As the "250 volt shop" is a part 
of the three- wire system with grounded neutral, a circuit breaker 
must be used on each side. 

Opening direct current motor and synchronous motor 
fields is likely to break down the insulation of the apparatus, 
and in the case of a d-c. motor, the motor will run away. Wher- 
ever binding posts and connectors, as used for rheostats and 
small fields, are employed, a length of unbroken insulation 
should be stripped from the end of the temporary field wire, 
so that the portion stripped can be passed through the binding 
post and bent back over the terminal. A complete loop is thus 
formed which prevents the circuit being broken, even though 
the clamping screw in the binding post or terminal works loose. 
It is not safe to insert in the binding post the bare end of a 
wire which has previously been used, since it may be fractured. 

When a motor field is wired through the field ammeter 
switch, the wire leading to the switch terminal and thence to 
the ammeter should be continuous, the switch simply serving 
to short-circuit the leads near the ammeter terminals. Motor 
field circuit breaking switches must be located so that they 
cannot be opened accidentally. The field switches must be 
provided with a holding clip, or other fastening. Single-pole 
switches must always be used in all field circuits. 

99 



In all cases, circuit breakers must be used for breaking 
direct currents of appreciable value. Oil switches must like- 
wise be used on all alternating current circuits, when currents 
and voltages of any magnitude are in question. Never break 
an alternating current circuit either by water box, or by 
an ordinary air-break switch, otherwise abnormal voltages 
may be produced and strain the insulation of the apparatus. 
All direct current generator and motor armature circuits must, 
therefore, contain a circuit breaker of sufficient capacity to 
open the maximum current delivered by the machine under 
test. When "feeding back" tests are made on direct current 
machines, two circuit breakers must be used, one in the supply 
circuit, and one in the motor-generator circuit through which 
the load energy is exchanged between the machines. 

All transformers with iron cases must have their cases 
grounded by a substantial wire, or cable, leading to ground. 
This lead must be substantially connected to the transformer 
case and to ground, so that it cannot be accidentally discon- 
nected. 

Temporary switches, circuit breakers, etc., should never 
be attached to a test table or switchboard which is permanently 
equipped. They should be mounted on rheostat stools, or 
temporary stands. All temporary cables and wiring must 
be properly insulated from iron floors, frames, and ground. 
High voltage alternating current lines must be carried at a 
sufficient height so that they cannot come in contact with 
men walking under them. This also applies to disconnecting 
and oil switches. Cables must be kept a sufficient distance 
apart to take care of the potential difference between them. 
They must be mechanically supported so they cannot drop 
from their fastenings to the floor. High tension wires must be 
carried to the testing table from the rear. They must not be car- 
ried over the heads of men working at the test table. All wires 
and circuits carrying more than 600 volts, must be regarded 
as high voltage. No one must approach closer than 1 foot to 
high voltage circuits, since many circuits possess sufficient 
capacity or voltage to arc over before contact is made. 

Starting Up 

Before starting a machine for the first time, the tester must 
assure himself that all instructions contained in Chapter 3, 
and in the preceding paragraphs have been rigidly followed in 
reference to the mechanical and electrical conditions, the wiring 
of the various circuits, lubrication, etc. The belt lacings must 
be watched to prevent them opening during test. Pulleys must 
be inspected by the regularly appointed Pulley Inspector 
to make sure they are securely fastened on the shaft and that 
they are mechanically strong. All keys, set screws, or other 
rotating parts which may catch in the clothing, or injure others 
must be properly protected. All keyways must be provided 
with covers or guards. All shafts carrying one-half of a solid 
coupling must have that part boxed in, so that workmen may 

100 



not come in contact with the sharp edges which usually exist. 
No loose articles must be allowed inside any rotating or station- 
ary parts. All belts must be guarded by substantial guards. 

If a machine has been standing for any length of time, 
before it is started again the same precautions must be observed. 
These points are strongly emphasized in reference to all ver- 
tical apparatus, where the danger of dropping things into a 
machine, while running, or of workmen leaving tools in danger- 
ous places on or about the machine is very much greater than 
with horizontal apparatus. 

When apparatus is first started it should be brought to 
speed very slowly and carefully watched to see that every- 
thing is correct as the speed increases to normal value. Reliable 
tachometers, or speed indicating devices must be used in starting 
to prevent a dangerous increase of speed. Oil rings must be 
examined at slow speed to see if they are carrying sufficient 
oil to the bearings. In the majority of cases, oil rings should 
turn when the machine is running at 34 normal speed, and 
should properly lubricate the bearings. 

The balance of the rotating parts should be carefully noted 
until the machine has reached its normal rated speed. If the 
apparatus does not run without vibration the matter should 
be reported as a defect. The vibration must be remedied 
before the test proceeds. Vibration due to the running of the 
machine may indicate lack of balance, whereas it may be really 
due to improper alignment, or to springing of the shaft. When 
unbalancing occurs in operating machines running above 1200 
rev. per min. correction must be made by dynamic balancing 
as in Chapter 3. 

Preparation for Heat Runs 

Heat runs are taken primarily to determine the amount of 
temperature rise on the different parts of a machine while run- 
ning under a specified load. This rise in temperature is measured 
either by the rise in resistance of the current carrying parts or 
by means of thermometers, or both. The results obtained by the 
rise in resistance, as a general rule, are used only as a check on 
the results obtained by reading thermometers placed on the 
different parts, the temperature rise of which it is desired to 
determine. Guarantees, except in special cases, are always 
based on the rise by thermometer. 

Thermometers should be carefully examined for broken 
mercury columns before being placed on a machine. They should 
not be inverted and in no case should they be placed on a 
machine so that the bulb is on a higher level than the 
other end. 

Before starting a heat run thermometers should be placed 
on the stationary accessible parts of the machine indicated by 
the Testing Record. Each thermometer should be attached with 
the bulb in contact with the part of which the temperature 
is required and should have the bulb covered with a sufficient 
amount of putty to secure it to the machine and to shield it 

101 



from being affected by the surrounding air. Extreme care must 
be exercised regarding the amount of putty so used, as too much 
putty is as bad as too little. Just enough should be used to 
do the work required. There should be no restriction of 
the natural windage of the machine or radiation from the coil 
whose temperature is being measured. 

Thermometers which are to register the temperature of air 
ducts should be so placed that the bulbs cannot make contact 
with the iron laminations while the machine is running. Ther- 
mometers which are liable to be shaken off by continued action 
of windage, or slight vibration, should be securely fastened to 
the machine. 

When placing thermometers on field coils, care should be 
taken tosee that they are not placed on the fiber strips protecting 
the outside terminals. These fiber strips run from one terminal 
to the other and form a non-conducting wall between the coil 
and its outside insulation, and thus do not represent the true 
temperature of the coil. Coils above the horizontal center 
line of the machine should be used as the top of the machine 
is usually somewhat hotter than the bottom. On small machines 
two thermometers will be sufficient on the coils, but larger 
machines should have at least four. 

One thermometer will be sufficient on the frame of small 
machines, but two or more should be used on the large units. 
At least two thermometers should be used on the laminations 
ard ducts of small machines, and at least four should be used 
on larger machines. 

Any large machine requiring a considerable floor space 
should have the room temperature taken at four or more different 
near-by points, and at a sufficient distance away so as not to be 
affected by the windage and radiation of the machine. 

The machine should be shielded from currents of air coming 
from adjacent pulleys, belts and other machines, as unreliable 
results are obtained when this is not done. A very slight current 
of air will cause great discrepancies in the heating results, con- 
sequently a suitable canvas screen should be used to screen the 
machine under test, or the machine causing the draught should 
be shut down. Great care must be used, however, to see that 
such screen does not interfere with the natural ventilation of 
the machine under test. Care must always be taken to see that 
sufficient floor space is left between machines to allow free 
circulation of air. 

During the progress of the heat run the different parts of the 
machine should be carefully watched for excessive heating of 
any part, including the bearings. A sufficient number of ther- 
mometers and amount of putty should be made ready to take 
all the final temperatures of the revolving parts after the machine 
is shut down, and the man in charge of the machine, if it is a 
large one, should obtain temporarily several extra men to help 
apply the thermometers and record the results. 

On shutting down, thermometers should be placed on all the 
revolving parts as specified on the Testing Record. 

102 



All small commutators should have at least two, and large 
ones at least six thermometers applied at different points 
extending the whole length of the commutator from the arma- 
ture risers to the outer end. 

The thermometers must be applied as speedily as possible, 
and the resistances of the various circuits measured immediately 
after the machine stops. If any thermometer shows an un- 
usually high temperature as compared with others it must be 
immediately checked by placing other thermometers on the 
same part. Reliable results depend directly upon promptness 
and speed, and nothing should be allowed to interfere with the 
carrying on of this work. To avoid repetitions of runs the 
machines must be shut down quickly. 

Readings should be taken of all thermometers every two 
minutes until they begin to fall. 

In calculating the rise of temperature the room temperature 
should be taken as the average of the last two readings recorded 
during the heat run. 

Temperature Coils 

In order more accurately to determine the temperatures of 
the inaccessible windings of large machines, coils of small wire 
known as "temperature coils" are sometimes imbedded in the 
slots with the main winding. The rise in temperature of the 
main winding is found from the rise in resistance of these tem- 
perature coils and, consequently, accurate measurement of the 
cold resistances of these coils is of the utmost importance. 
During the heat run, readings should be taken of the resistances 
of these coils at the same time that the thermometer readings 
are taken. All readings must be very carefully made as a small 
error made in the resistances of these coils makes a very appre- 
ciable difference in the final temperature obtained. The rise 
in temperature mav be calculated from the formula given on 
page 112. 

OBSERVATIONS AND COMMENTS DURING OPERATION. 
REPORTING AND CORRECTING DEFECTS 

On all Testing Records a number of questions are given 
concerning the operation and condition of the machine during 
the test, which should be intelligently answered by the men 
conducting the test. 

A close watch should be made for undue heating of bearings. 
While running under load, no bearing should rise more than 40 
deg. cent, above the room temperature. In case such a rise 
occurs, the bearing should be scraped and the test repeated. Any 
machine showing a bearing temperature rise of 25 deg. cent., 
during an "equivalent load" run, should have the run continued 
till bearing temperatures are practically constant, unless the 
temperature continues to rise rapidly. In any case, note should 
be made if the bearing temperatures rise above these limits and 
the fact should be reported as a defect. 

103 



A record should be made of any oil throwing or leakage 
during test, and the matter reported at once. In the case of 
oil throwing on d-c. machines, the test should be discontinued 
until the defect is remedied. 

All covers must be assembled in place so that it is impossible 
for any foreign matter accidentally to get into the machine. 

All staging around machines must be substantial and secure. 

End play should be tried both with and without field on 
the machine. This matter should be recorded on the Record 
Sheet. If the end play is. defective it may be repaired as given 
on page 96. 

During a heat run, machines set upon shop blocking should 
have the blocking and holding-down bolts examined at least 
every 24 hours to prevent the machine from pulling over or the 
bearings from loosening. 

Any connections not checking with the connection print or 
wiring diagram should be reported. 

All machines should be carefully watched for any unbalanc- 
ing or change in alignment. A defect of this nature may appear 
after the machine has been running for some time even though 
the balance and alignment may have seemed perfect at the 
beginning of the run. 

Record should be made of binding bands, commutator 
shrink ring or any other part running out of true. 

Commutators sometimes become noisy during operation, 
due to brush friction. This may be remedied by a slight occa- 
sional lubrication of the commutator surface. The noise may 
be due to the brushes chattering, in which case no lubrication 
must be used, but the defect reported at once. Chattering 
may be caused either by poor commutator surface or an improper 
setting angle of the brushes. 

One or two brushes may glow and become very hot on a 
stud carrying a number of brushes, while the other brushes run 
cool and without sparking. This is known as selective com- 
mutation and is due to difference in brush pressure, composition 
or contact resistance which cause some of the brushes to carry 
more than their share of the current, thus overheating them and 
giving poor commutation. In order to remedy this difficulty, 
it is usually necessary to change either the brushes or brush 
pressures, or possibly both. 

The brushes should be examined to see that they do not 
stick in their holders. 

Collector rings with rough joints, eccentric collector rings 
or ones running out of true should be reported at once. 

Unless the line circuit of a machine or the circuit supplying 
excitation to the fields is grounded, grounds developing in the 
armature, fields, or fittings during test may not at once become 
apparent. During the high potential test any defect of this 
nature is readily shown, however, and should be reported at 
once in order that repairs may be made immediately. 

The spacing and alignment of field poles, especially in the 
case of com mutating pole machines, should receive the most 

104 



careful attention. Poor alignment is usually indicated when 
the air gap is measured. 

The checking of polarity (see page 111) at once indicates 
the reversal of any field coils. 

In three-phase machines the reversal of any phase will 
cause a considerable unbalancing in the voltage across phases. 
The reversal of one coil will be shown in a similar manner, 
but the unbalancing is not so pronounced. In quarter-phase 
machines these defects will be shown by the phase rotation 
test only. See page 172. The test of balancing voltage and cur- 
rent and of phase rotation should, therefore, be carefully taken. 

Stationary Apparatus 

The instructions already given in reference to rotating 
apparatus very largely apply to stationary apparatus. The 
following points must also be carefully observed in testing the 
latter, including transformers, regulators, compensators, switches, 
relays, etc. 

Careful inspection must be made for mechanical or elec- 
trical defects when preparing stationary apparatus for test. 
The precautions already given in reference to wiring should be 
followed. All valves, tripping devices, contacts and insulation 
should be examined. 

Wherever cases or receptacles are oil filled for insulation 
purposes, see that the proper amount of oil is put into them 
before test. During the test the tanks and receptacles must 
be carefully inspected for oil leakage, due to blow holes in 
castings, oil plugs, oil gauges, or due to siphoning through the 
leads. Adjustments of springs, weights, contacts, gauges and 
air gap clearances must be made before testing, so far as is 
practicable. Xo metallic particles must be allowed to drop or 
be thrown into transformers, regulators, etc., during test; 
otherwise breakdowns of insulation may result. 

When testing stationary apparatus, it is rarely possible to 
tell from inspection whether the apparatus is "alive" or not. 
Hence there is all the more reason, on high voltage apparatus, 
to make use of signs and barriers, to eliminate danger and pre- 
vent shocks. 



105 



CHAPTER 5 

TESTING RECORDS 

For the purpose of recording the results of standard tests, 
various Testing Records are used to suit the different classes 
of apparatus. Before a standard test is made, the tester must 
provide himself with one of the Testing Records. He should 
immediately fill in all blanks and headings, with all the data 
concerning the machine which can be entered before the test 
is started. All entries must be made at once upon the Testing 
Record and never on "scrap paper." These Testing Records 
(which should contain all the results of the standard test) 
must be checked at the conclusion of each test to insure con- 
sistency of readings and that full and complete explanations 
have been made concerning the machine under test. 

One man is appointed in each section to approve the results 
of each individual test immediately upon its completion. In all 
cases the written approval of this man must be obtained for 
each test before the next test is started. 

The completeness of these records is of the greatest impor- 
tance, since they are used when passing the machine for ship- 
ment and are finally filed in the Data Department, where they 
are accessible for reference for the Designing Engineer and 
others who desire to know the characteristics of the particular 
machine. It is, therefore, necessary to make accurate, neat 
and orderly entries on the Testing Record, and supplement 
them with sufficient data fully to inform any one who has not 
personally taken part in the test. Then, if reference is made to 
them afterwards, no question can arise as to the meaning of 
any of the readings or observations made. 

In general, the Testing Record is intended to be a complete 
and accurate history of the individual machine while in test 
and, therefore, every effort must be made to carry out this 
idea. 

Special tests must be recorded on special Record Sheets. 
As these tests are special and often involve new or peculiar 
conditions, careful notes and explanations, with diagrams if 
necessary, should be entered to make clear the conditions under 
which the test was conducted. 

The date of making the test, together with the name of the 
individual making it must always be recorded on all Testing 
Records and Record Sheets. In addition, whenever exhibition 
tests are made for our own Engineers, or for a customer's Engineer 
the Record Sheet must give the names of the Engineers who 
witness the test. Records of tests taken under the direction 
of a customer's Engineer must be plainly marked so that they 
may be distinguished from any other tests which may be taken 
on the machine. It is frequently necessary to furnish the cus- 
tomer with "certified copies" of tests in lieu of his sending an 
Engineer to witness the tests and check up the guarantees. 
Wherever Engineering instructions request "certified copies" 

106 



of the test, all the necessary tests and information must be 
recorded on the Record Sheet so that "certified copies" can be 
made, demonstrating that all guarantees have been met. 

The reasons for all check tests should be plainly stated on the 
Testing Record. 

When tests have been finished, all records in reference to 
them are sent to the Calculating Room, and such calculations 
made as required. Curves showing the characteristics of machines 
are plotted and filed with the corresponding Record Sheet. It 
is the function of the Calculating Room also to check up results 
on the Testing Records with those of duplicate machines already 
shipped; and, where necessary, to refer Testing Records on 
newly designed machines to the Engineering Department for 
their approval before passing the machine for shipment. As 
soon as the Calculating Room is assured, that the test proves 
that a given piece of apparatus is satisfactory and has the 
characteristics required for our guarantees, it approves the 
Testing Record and the machine is listed on the "Daily Test 
Report." 

The "Test Report" is issued daily, copies being sent to all 
persons interested in the shipment of the machine. It is the offi- 
cial notification that the apparatus is satisfactory in all respects 
and may be shipped. 

The majority of apparatus tested is listed upon this "Test 
Report." Certain small mechanisms and parts which only 
require a slight electrical test are passed for shipment, bearing 
the Testing Department stamp only, to show that they have 
been officially tested. 

Since the system of passing apparatus is largely founded 
on the test records, it is essential that these records be com- 
plete in every detail. 



107 



CHAPTER 6 

METHODS OF CONDUCTING STANDARD 
TESTS 

In the manufacture of armatures and fields for electrical 
apparatus, many of the "faults and weaknesses" of material 
and errors of workmen can be disclosed by what may be termed 
"stationary testing." Faults and weaknesses may arise as 
follows: Through a wrong application of insulation, or through 
mechanical, faults in it. The use of wrong material for con- 
ductors, leads, etc. Wrong assembly or connections — workmen's 
mistakes. 

Direct current armatures are tested for grounds, short-cir- 
cuits, open -circuits, and high resistance joints before being 
sent to the Testing Department. In testing for grounds a 
high potential is applied between winding and core; the potential 
depending upon the class of apparatus tested. When a ground 
develops in test, if it cannot be located by inspection it must 
be referred to the Armature Department. In no case is it to 
be located by smoking the insulation. 



/K 




-0-31 



Fig. 47 
TESTING FOR GROUNDS 

If a low resistance ground has developed it may be quickly 
and accurately located by the following method: A low voltage 
current is passed through the armature winding from a com- 
mutator bar to the one adjacent to it, which is sufficient to 
give a readable deflection on a galvanometer or milli- voltmeter 
(as shown in Fig. 47). A line is connected to a galvanometer 
to ground, the other galvanometer connection being placed 
on one of the commutator bars. Then pass the supply and 
galvanometer leads from segment to segment, until a full 
deflection is obtained and zero reading when the leads are 
moved one segment further. The grounded coil then lies 
between the bars, for which full deflection was obtained. 

108 



A "bar to bar" test is usually made to disclose short-circuits 
open-circuits, and other similar faults. For this test the wind- 
ings connected to two adjacent commutator segments have 
their resistance measured by the "drop of potential method," 
as indicated in Fig. 48. Storage batteries should be used and 
a special electro-magnetic D'Arsonval galvanometer. With this 
arrangement readings can be obtained rapidly, as the instrument 
is "dead beat." 

Measuring the ohmic resistance of the winding will some- 
times reveal a wrong connection, which, on a bar to bar measure- 
ment, would give a uniform deflection all around the commutator. 
Series or wave windings may sometimes have all the conductors 
joined in series, but in the wrong order, so that the armature 
is inoperative. In the case of multiple or lap windings, double, 
triple or even quadruple spiral re-entrant windings are possible, 
whereas a single spiral is required. In taking a resistance 
measurement for brush to brush or a running resistance of 
the armature, see that the measurement is made from the 
proper commutator segments. For multiple or lap windings, 
the resistance measured from diametrically opposite points 
divided by half the number of poles squared will give the true 
running resistance, while with a series or wave winding the 



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TESTING FOR OPEN CIRCUIT 



resistance should always be taken at points 180 electrical degrees 
apart. For example, take a four-pole armature with a lap 
winding and 360 commutator segments. This should have 
its resistance measured between bars Xo. 1 and No. 181. The 
resistance divided by four will give the running resistance. 
With a wave winding on the same armature, the resistance 
measurement should be taken between bars No. 1 and No. 91, 
this resistance being the true running resistance. 

Alternating current armatures and fields are similarly tested 
for grounds, short-circuits, open- circuits, wrong connections, 
polarity, etc. In testing for grounds the same methods and 
similar apparatus are used as for direct current machines, 
except that with alternating current the voltages generated 
and used are usually higher and, consequently, the testing 

109 



voltages are correspondingly higher and greater care must be 
taken in testing. All high potential tests must be made with 
carefully calibrated electrostatic voltmeters that have been 
checked with a spark gap. The testing equipment should be 
as near the apparatus as possible, since the additional capacity 
of testing lines may raise the voltage at the receiving end much 
above that at the generating end. Unless this precaution is 
taken, excessive voltages may be applied which may damage 
the insulation. In case a ground develops a resistance measure- 
ment will generally locate the point at which it occurs, unless 
each phase has two or more multiple circuits. In the latter 
case it may be more readily located by opening one or more 
cable joints and separating the circuits. 

A measurement may then be taken in the following manner: 
First, measure the resistance of the grounded circuit or phase. 
Second, measure the resistance to ground by connecting one 
line to ground. Third, measure the other end of the resistance 
to ground, by connecting one measuring line at the other ter- 
minal of the phase and one to ground. If all measurements 
have been accurately made the sum of the second and third 
will be equal to the first, and the location of the ground will 
be as far from one terminal as the measured resistance from 
that terminal to ground is of the total resistance of the circuit. 

This test is shown in Fig. 49, which represents a single 
circuit, or phase, of an alternating current machine, with a 



I 






Fig. 49 
TEST FOR GROUNDS ON AN A-C. ARMATURE 



ground as shown. If the resistance between A and B is one 
ohm, between A and G 0.35 ohm and between B and G 0.65 
ohm, the location of the ground is 35/100 of the distance 
between A and B, from A. As 10 coils are in the circuit the 
measurements show that the fourth coil is grounded, counting 
from A. 

In the case of an alternating current winding the ohmic 
resistance measurement will not always detect a wrong con- 
nection, such as a reversed coil, pole section, or phase; since, 
although the copper resistance would be measured correctly 
the total winding might be partly reversed and, therefore, 
inoperative. Such faults may be discovered by a polarity or 
impedance test, with alternating current. For this purpose a 
:single-phase current can be used, since a reading may be taken 

110 



on the different circuits, or between pairs of terminals succes- 
sively by shifting the testing lines until the whole windings 
have been tested. 

Short-circuited coils on moderate size machines can be 
readily tested by using a wound electro-magnetic yoke excited 
with alternating current. This yoke is dropped over a portion 
of the armature coil after the coils have been placed in their 
slots. The yoke and armature form an alternating current 
transformer, "with the yoke winding as primary, and the arma- 
ture coil as secondary. If there is a short-circuited turn, layer 
or coil in the armature, the magnetizing current in the yoke 
winding rises. If the current is maintained a short time, the 
insulation on the short-circuited section will warm up appreci- 
ably, or burn sufficiently to indicate the defective coil. 

On larger size alternator armatures, tests may be made for 
short-circuits by passing alternating current through the 
armature coil itself. In this case it is usually necessary to 
increase the reactance of the coil by placing a magnetic bridge 
over its armature slots after it has been assembled in the core. 

The above tests may be made with the apparatus at rest. 
The Armature Department, therefore, uses them for detecting 
faults and correcting them before delivering the parts to the 
Testing Department. These faults can be more readily cor- 
rected when apparatus is being wound, with a resulting saving 
in time and cost. It is, however, sometimes necessary to test 
by these methods, after apparatus has been received in the 
Testing Department, in order to locate faults which have 
developed later. 

As soon as the spools are assembled on a machine and before 
the frame is taken from the spool assembly stand the windings 
should be tested electrically for resistance and high potential. 
They should also be tested for polarity of the poles by exciting 
the field coils. These tests check the assembly of spools and 
their position upon the frame. In testing field coils for polarity 
all field windings must be tested separately to ascertain that the 
series, shunt and commutating pole windings are wound and 
assembled so as to give the required polarity. Polarity may be 
tested by use of a compass, but the compass must not be carried 
too near to the poles, as it may be demagnetized, or even reversed. 
To test for the opposite polarity of alternate poles, bridge two 
pole tips with a piece of soft iron. If the polarity of the poles 
differs the piece will be strongly attracted, whereas if the poles 
are of the same polarity much less attraction will be exerted. 

Drop on Spools 

With a given current flowing through the field the voltage 
drop on any one spool of a direct current machine should in 
no case be more than 4.5 per cent higher or lower than the 
average drop, and on alternating current machines no spool 
should vary more than 7 per cent either way from the average. 
If the drop is outside of these limits, the matter should be 
referred to the office for instructions. The field spools for 

111 



alternating current apparatus are assembled on the field spider 
in the Armature Department, hence it is necessary to take only 
a resistance measurement per spool before using them for a 
test. In recording drop on the spools of alternating current 
machines, they should be numbered in a clockwise direction 
facing the collector end, and beginning at the spool next to the 
opening in the field for spool No. 1. 

In direct current machines spool No. 1, either main or corn- 
mutating is always the top spool or the next adjacent in a clock- 
wise direction facing the commutator end. 

Resistance 

When testing a machine a very careful record must be kept 
of the resistances of all windings. Most armatures when 
delivered to test are fitted with equalizer rings which make it 
impossible to obtain the true armature resistance. The Arma- 
ture Department's tag attached to the armatures when received 
in the Testing Department gives the armature resistance which 
was obtained before the connection of the equalizer rings. The 
tester must, therefore, record on the Testing Record the measure- 
ment of resistance from this tag. The armature resistance is 
rarely measured in the Testing Department. Such cases are 
specified when required. The shunt field resistance is obtained 
by the "drop method," using an ammeter and voltmeter. This 
measurement is required on each machine before a test is started. 
For measuring the series field resistance a special galvanometer 
measuring set must be used, with which the various testing 
sections are provided. As a considerable amount of the resist- 
ance of a series field may consist of the contact resistances 
between the spools, all connections must be carefully cleaned and 
clamped tightly together, before taking the resistance. 

After the heating test on any machine, the resistances of 
the various parts are again measured and the rise in temperature 
may be calculated by the following method: 
Let Rh = hot resistance of copper measured at the temperature 

h- 
Rti = cold resistance of copper measured at the temperature 

h. 

Then * 2 = (238+*i) -^7 -238 
Kt\ 

The rise obtained from this formula should then be corrected 

according to the standard rules of the A.I.E.E. for variations 

from 25 deg. cent, in the observed room temperature. 

Insulation Resistance 

A measurement of the insulation resistance is occasionally 
taken upon direct current machines and alternators. The 
government requires this measurement in most cases. An 
insulation resistance measurement is frequently taken on 
alternators of 2300 volts and above. On commercial apparatus 
generally, the measurement of insulation resistance, however, 
is unnecessary, since the materials used have ample dielectric 

112 



strength and the slight leakage which a low insulation resist- 
ance would indicate is unimportant. This test when required 
is taken by the "d-c. voltmeter method of measuring high resist- 
ance" as given on page 42. In case the insulation resistance is 
lower than required, due to dampness, the machine should be 
baked either by the method described for making equivalent 
load tests (page 144) or by placing the machine in a baking oven. 

High Potential Test 

This test is taken by applying an alternating voltage between 
the various windings of a machine and from the current carrying 
parts to ground. Fig. 2 shows the connections for one of the 
standard high potential testing sets. Unless otherwise specified 
all high potential tests should be taken as given on the Standing 
Instructions for the machine in question. When the high poten- 
tial test is applied to a moderate or large sized machine or piece 
of apparatus, such machine must be entirely surrounded by 
white tape and should have placed on it in a conspicuous place 
the standard high potential signs to make doubly sure that no 
one comes in contact with it. A sufficient number should stand 
guard around it to make sure that no one is injured. 

On small apparatus the standard high potential signs should 
be used and but one man need stand as guard. Small machines 
need not be surrounded with white tape. 

After finishing the high potential test all oil and disconnecting 
switches must be opened before the high potential testing cables 
leading to the apparatus are handled. All temporary and high 
potential testing cables must be disconnected from the testing 
transformers or high voltage source at the conclusion of the test. 

Adjustment of Speed Limiting Device 

Many d-c. machines are equipped with a device for limiting 
the speed in case of loss of field or any other condition which 
might cause excessive speed. These devices must be adjusted 
to operate at 15 per cent above the normal speed of the machine 
under test (10 per cent for shop machines). This device is a 
centrifugal device in which a revolving weight acts against a 
spring and operates a switch connected in the circuit of the low 
voltage trip coil of the circuit breaker. 

Figs. 51a and 51b give diagrammatic views of the latest type 
of this device. In order that it may operate properly the follow- 
ing adjustments must be made: 

With the weight moved outwards to the maximum distance, 
a clearance of ye in. as shown in Fig. 51b must be allowed between 
the centrifugal weight and the link when the switch is open. 
This clearance must be allowed in order to prevent the weight 
from hammering the switch after it has been forced open. 
With the switch blade wide open and with the weight at its 
maximum distance outwards, there must be y& in. clearance 
between the nearest point of the switch and the centrifugal 
weight. A clearance of 34 in. must be allowed between the 
switch blade and the clips when the switch blade is in its extreme 
"out" position, as shown in Fig. 51b. 

113 



The adjustments of the clearance of the switch and centrif- 
ugal weight can be obtained by finishing their respective stops 
(on the short end of the switch and the hook shaped stops on 
the ring), to the proper dimensions. If too much material has 
already been removed from the stop, it may be drilled and tapped 
for a screw or plug which can then be finished to the proper 
dimensions. 

All of the clearances given are the minimum that are obtained 
when the weight is rotating. 

After these clearances have been adjusted, the spring should 
be adjusted, if necessary, so that the centrifugal weight strikes 
the switch and forces the switch blade from the clips when the 
speed has reached the specified limit. The springs are adjusted 




Fig. 50 
SPEED LIMITING DEVICE (EARLIER TYPE) 

so that the weight operates on the switch when the speed has 
risen 15 per cent above normal. The method of spring attach- 
ment and therefore of adjustment will be clear from the figures. 

The switch shown in Fig. 50 is arranged to short-circuit the 
low voltage trip coil of the circuit breaker and should be adjusted 
with the clearances shown in Figs. 52a, b, c. In this case the 
revolving weight drives the switch blade into the switch con- 
tacts. 

Figs. 52a, b, c also show diagrammatically a type of 
switch which is adjusted by varying the notch in which the 
loose end of the spring is placed. The number of the notch in 

114 




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DETAILS OF SPEED LIMITING DEVICE (LATER TYPE) 



115 




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Fig. 52c 
DETAILS OF SPEED LIMITING DEVICE (OLD TYPE) 



116 



which correct adjustment is obtained must be recorded, and 
the speed at which it trips; also the tripping speed and number 
of the notch on each side of the correct one. The notches are 
numbered beginning at the one nearest the pivot. 

In adjusting any speed limiting device several check readings 
must be taken at the final position to make certain that the 
device is set at the proper point. 

Adjustment of End Play Device 

Many machines, especially synchronous converters, are 
equipped with an end play device to cause an even wearing of 
bearings, commutator and collector rings. These devices are 




Fig. 53 
MAGNETIC END PLAY DEVICE 

of two types, viz., magnetic and mechanical. Before any adjust- 
ments are made great care must be used to see that the machine 
is perfectly level, that it floats in the mid position of its end 
play with field on, and that it has the correct amount of end 
play. 

The magnetic end play device, see Fig. 53, causes the armature 
to oscillate by the same principle as is used in an electric bell. 
It should be wired as shown in Fig. 54, using a source of supply 
whose voltage equals the normal voltage of the machine under 
test. To adjust the device set contact (A) by means of the 
thumbscrew (T) until it firmly touches contact (B). This 
is done with the armature in the mid position of its end play. 
When the contacts come together the circuit is closed through 
the coil and the electromagnet pulls the end of the shaft toward 
it. When the shaft comes toward the magnet it pushes the rod 

117 



(R) against the arm carrying contact (B) which opens the 
circuit, releasing the magnetic pull on the end of the shaft so 
that the armature is pulled back in the other direction by the 
field of the machine. The momentum of the armature carries 
it beyond the mid position of the end play and the contacts 
come together again. The pull of the electromagnet is not 
exerted fully until the armature has traveled away from the 
device some distance beyond the mid position. The pull is 
then established and causes the armature to return to mid 



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CONNECTION DIAGRAM FOR MAGNETIC END PLAY DEVICE 



position. This cycle is then repeated. A rheostat is provided 
to adjust the magnetic pull of the device to that of the fields, 
so that the armature may oscillate the full distance of end play 
allowed without bumping the bearings. After final adjustment 
has been obtained, the amount of resistance included in the 
rheostat should be measured and recorded on the Testing Record. 

A condenser is connected across the contact to suppress the 
spark when the circuit is opened. 

The bushing through which the push rod passes should not 
be lubricated, as it is provided with specially prepared graphite 
for self-lubrication. 

The mechanical end play device is shown in Fig. 55, and 
consists of a ball running in a raceway held in a block which is 
held in a shell. This shell is screwed into a three armed casting 
which is bolted to the end of the pillow block of the machine. 
This ball makes contact with a plate on the end of the shaft 

118 



of the machine. The shell in which the raceway block is held 
should be screwed into the position at which the ball will just 
make contact with the plate when the armature is in the mid 
position of its end play. The ball must be in its lowest position 
and the spring which" is in the shell must not be set up tight 
but must have sufficient play to take up the force of the end 
thrust. As the center line of the raceway block is at an angle 



Fig. 55 
MECHANICAL END PLAY DEVICE 



with the center line of the shaft, the friction between the ball 
and plate will cause the ball to be carried up and during the 
revolution it will throw the shaft its full distance. The ball 
will then fall back and the pull of the field will cause the arma- 
ture to return and the cycle to be repeated. Adjustment should 
be made of the tension of the spring so that the armature will 
swing through the range of its end play and yet not bump the 
bearings. It may be necessary to change springs. When the 
exact position of the ball has been determined, the shell may 
be held in place by screwing down the plug in the side of the 
three armed spider. 

Saturation 

In order to ascertain the characteristics of the magnetic 
circuit, a test known as "saturation" is made. The character- 
istic curve may be obtained by either of the following methods: 
"generator saturation," or "motor saturation." 

119 



Generator Saturation 

The test usually made is "generator saturation." To 
obtain a saturation curve by this method, the machine is driven 
as a generator, preferably at normal speed. If, however, 
a set of readings is known for one speed, they can be obtained 
for any other by direct proportion. Hence a saturation curve 
taken at any constant speed at once gives the saturation curve 
at any other speed. The brushes of direct current machines 
should always be set on the neutral point and the machines 
run preferably at no-load speed when taking a no-load saturation 
curve. 

In taking a saturation curve on polyphase alternating cur- 
rent generators, a reading of the voltage across each phase 
must be taken at normal field current, to see if the phases 
are properly balanced. If they do not balance, they must be 
made to do so. On synchronous converters careful readings 
must be taken of the direct voltage, as well as the alternating 
voltage between all phases with the field excitation giving 
normal voltage. The phase voltages must also be closely 
balanced. 

The usual method of taking a generator saturation curve 
is to hold the speed constant, and then increase the field current 
step by step until at least 125 per cent of the normal voltage 
of the machine is reached, taking readings at each step simulta- 
neously, of volts armature, volts field, and amperes field. After 
reaching the maximum value of the field current, without open- 
ing the field, reduce the current gradually in four or five steps, 
and again take readings to determine the value of the residual 
magnetism at various points along the curve. Special care 
must be taken to insure accurate readings at and above normal 
voltage, since with alternating current generators, this is the 
portion of the curve used for calculating the regulation under 
load. Whenever saturation curves are taken, a record of the 
air gap from iron to iron must be made upon the Record Sheet, 
together with the armature and field specifications. 

Motor Saturation 

When it is inconvenient or impossible to drive the machine 
as a generator, a "motor saturation " may be made. In this case 
the machine is operated as a free running motor. The driving 
power must be furnished from a variable voltage circuit. A 
certain voltage is impressed upon the armature and the motor 
field weakened or increased in the case of direct current machines 
to give normal speed, and a record made of the volts armature, 
amperes armature, amperes field, volts field, and speed. The 
starting voltage should be at least 50 per cent lower than 
the normal voltage of the apparatus. The applied voltage 
at the armature should be increased by steps to 25 per cent 
above normal value, and the field increased correspondingly to 
keep the speed constant, the same readings being recorded at 
the various steps as before. Readings should also be taken at 

120 



three or four points as the impressed voltage and field current are 
lowered to approximately the values at the beginning of the test. 
Care should be taken when testing direct current apparatus, 
as unstable electrical conditions may develop, and excessive 
speeds result. The circuit breaker in the armature circuit of 
the motor driving the machine must, therefore, be accessible 
to the tester reading the speed. 



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SATURATION CURVE ON A 500 KW., 600 VOLT, 20 POLE, 360 R.P.M. 

3-PHASE, 60 CYCLE, A-C. GENERATOR 



On alternating current apparatus, the machine is run as 
a motor and the impressed voltage varied as already described. 
The speed is independent of the motor field in this case, and 
instead of regulating the motor field for speed it should be 
regulated to give mimimum input current at each voltage. 
Readings should be taken of voltage impressed, amperes arma- 
ture, amperes field, and volts field. With induction motors it is 
only necessary to impress variable voltages at constant fre- 
quency and record readings of impressed volts armature, 
amperes armature, and speed. 

121 



The calculation of saturation tests is very simple, as it 
consists only in applying instrument correction factors and 
ratios, and plotting upon coordinate paper, volts armature 
as ordinates and amperes field as abscissae. Fig. 56, and Calcu- 
lation Sheet No. 1, show the results of a saturation test made 
by either of the above methods. 

Core Loss 

Three methods are used to measure the core losses on rotating 
direct current apparatus and alternating current synchronous 
apparatus. They are known as follows: "running light core 
loss," "belted core loss," and "deceleration core loss." 

The following conditions must be obtained with direct current 
apparatus in order to give satisfactory results: Brushes must 
be shifted on the commutator to the mechanical neutral point. 
They must have their normal tension and the commutator 
must be clean, so that the normal operating commutator and 
brush friction values are obtained. This test, wherever pos- 
sible, must be made after all the others have been finished, 
in order to have a glossy commutator with its surface in good 
operating condition. The driving power should be supplied 
from a variable voltage circuit that is not subject to sudden 
fluctuation. Readings must not be taken when the rotating 
parts are accelerating or decelerating. 

Running Light 

This test is made by running the machine free as a motor. 
It is made on most d-c. generators and motors which are given 
a running test and occasionally on alternating current syn- 
chronous apparatus. 

When "running light" tests are made on direct current 
generators, the observations must be made with full load field 
flux. The potential applied to the armature must be equal 
to the normal rated voltage of the generator increased by the 
IR drop in the armature at full load. With this voltage im- 
pressed, the field current is varied until normal speed is obtained, 
when careful readings must be made of armature current, 
armature voltage, field current, field voltage and speed. 

If the machine in test is a direct current motor, the voltage 
applied to the armature should be equal to the normal rated 
voltage of the motor, less the IR drop in the armature under 
full load. The field current is then adjusted to give normal 
speed and electrical and speed readings taken, as outlined 
above for direct current generators. 

The power supplied to machines running free will equal 
that absorbed in bearing friction, brush friction, windage, 
and core loss, when the armature PR losses have been sub- 
tracted. 

In making records of these tests, the Testing Record must 
clearly show whether the running light current consists of the 
armature current plus the shunt field current, or whether it 
is the armature current alone. To check this point, open 

122 



the armature circuit with the shunt field circuit closed, and 
note whether any current is indicated on the ammeter reading 
the power supplied. If no current is indicated, the reading 
indicates the armature current alone, otherwise, the running 
light current is equal to the sum of the armature and field 
currents. To obtain ''running light" core loss tests, only a 
single field winding must be used for excitation; this must be 
a shunt field winding. 

In the case of series wound motors the field should be sepa- 
rately excited and extreme care should be taken to see that the 
motor does not lose its field. 

In order to obtain running light core loss upon alternating 
current synchronous machines (in which class synchronous 
converters are not included as the core loss test on these ma- 
chines is similar to that on direct current machines), they should 
be operated as synchronous motors at the proper frequency and 
rated voltage. For the best results, both frequency and voltage 
must have a steady value. 

With normal voltage on the armature, the direct current 
field should then be varied until minimum armature current 
is obtained. Readings should then be taken of amperes and 
volts of all the phases. At minimum input current unity 
power-factor is obtained and, therefore, the power to drive such 
machines will be the volt-ampere input. Wattmeters may 
be used in addition to check the volt-ampere readings. This 
measurement includes friction and windage losses, together 
with open-circuit core loss, plus the I 2 R loss in the armature. 
If the value of the core loss need not be separated from the other 
losses, the test is useful for checking up full load efficiencies. 

Belted Core Loss 

By means of the ' ' belted core loss' ' method the core loss can be 
separated from the bearing friction, brush friction and windage. 
A small direct current motor is used to drive the machine under 
test as a generator at its rated speed. A belt drive between these 
machines is most commonly used, but wherever great accuracy 
or a high speed is necessary, direct drive by means of a coupling 
is often used. 

The driving motor for this test should be such that good 
commutation is obtained for all loads required by the core loss 
test with a fixed setting of the brushes; and with the maximum 
volts on the machine under test, it should carry not more than 
50 per cent of its normal rated capacity. Ordinarily a good rule 
to follow is to select a motor, the rated capacity of which is 
approximately 10 per cent of the rated output of the machine 
under test. When the brush setting to give the best possible 
commutation at all loads has been obtained, the brushes should 
be left in that position throughout the test. The commutator 
surface should be in first class condition and should have the 
brushes closely fitted to it. 

The belt should be of minimum width and weight to carry 
the load without slipping. When testing motor-generator sets, 

123 



synchronous converters and other machines that do not require 
belts in practice, the tension of the belt must be kept as low as 
practicable so that the bearing friction is not increased on account 
of belt pull. Endless belts should always be used in preference 
to laced belts. 

The diameter of the pulleys should be so selected that the 
driving motor will run at or near its rated speed when the 
machine under test is running at its normal speed. 

The driving motor should have its field separately excited 
from a constant source and other wiring so arranged that readings 
may be taken of amperes armature, volts armature, amperes 
field and speed. The volt-wires should be firmly attached to 
brushes on two adjacent studs. The brushes so used should be 
insulated from the holders so that the true volts armature may 
be obtained. Previous to starting the test, careful resistance 
measurements must be made of the armature of the driving 
motor. 

The machine under test should be wired as a separately 
excited generator with provision for reading volts armature, 
volts field, amperes field and speed. 

The test should then be carried out as follows: The field 
of the driving motor should be adjusted to about normal value 
and held constant, and the speed regulated by varying the 
voltage applied to the armature terminals. Careful readings 
should be taken to make sure that no belt slipping occurs. This 
is done by taking simultaneous readings of speed of both the 
driving motor and the machine under test: (a) with no field on 
the machine under test, (b) with normal field excitation. The 
two readings of speed should be identical. The machines 
should be run a sufficient length of time to allow the friction 
to become constant. This will be the case when the input to 
the driving motor becomes constant when driving the machine 
under test without any field excitation. 

Throughout the entire test, readings must be taken at abso- 
lutely constant speed when the rotating parts are neither accel- 
erating nor decelerating. 

Readings should be taken as follows: 

(a) Take the input to the driving motor with no field on the 
machine under test and with all brushes down on the commu- 
tator. 

(b) Take the input with field on the machine under test 
to give normal volts with all brushes down on the commutator. 

(c) Take the input with all brushes raised from the com- 
mutator and with the same field current in the machine under 
test as for the preceding reading. 

(d) Take the input with all brushes raised and with no field 
on the machine under test. 

The difference between the first and fourth readings is brush 
friction. The difference between the second and first readings 
and also the difference between the third and fourth readings is 
core loss. The core loss should be the same with the brushes 
down as with the brushes up, and the two results obtained 

124 



should check within 6 per cent before proceeding with the test. 
Starting with zero field on the machine under test observations 
of the input to the driving motor should be made at various 
values of the field up to that which will give 125 per cent normal 
voltage, and at least half the readings should be taken between 
90 per cent and 110 per cent of the normal voltage. 

The "friction, reading" with zero field excitation on the 
machine under test should be repeated at least three times during 
the progress of the test; namely, at the beginning, again near 
the mid point of the curve and finally at the end of the test. 











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it in 




























/ 




rl 
























/ 






























/ 






^o 
























/ 






* <? 






















y 






• i 
























/ 






! 






















/ 




























w 










! 


















Nj> 












































_ 


























































1 


o 




i 


ft 


y 


TT^ 


* 


y 


^ 


J 


V 


h- 


<=>? 


yj 


44- 1 



Fig. 57 

OPEN CIRCUIT CORE LOSS ON A 500 KW., 600 VOLT, 20 POLE, 360 R.P.M. 

3-PHASE, 60 CYCLE, A-C. GENERATOR 



As the amperes field of the machine under test are increased 
the volts armature of the driving motor should also increase 
because of the increased IR drop in the armature. 

The driving motor should then be unbelted and a "running 
light " reading taken on it as follows: Without changing the brush 
shift hold the same amperes field as was held during the core loss 
test and take a reading of the input to the motor to give the 
same speed as was read on the driving motor at the beginning 
of the test. The volts armature should be lower than for anv 
reading taken during the core loss test. 

To check the results of the core loss as the test proceeds the 
power input to the driving motor required bv the core loss at 
a given excitation should be plotted agains't volts armature 
generated. This should give a curve similar to Fig. 57. 

Correcting the motor input at the various field strengths 
by deducting the PR loss in the armature of the driving motor 
and subtracting the power input to the driving motor with zero 
field on the machine in test, the core loss is left corresponding to 

125 



By subtracting the "running light " 
input to the driving motor from the input with zero field on the 
machine in test, the bearing friction and windage losses of the 
machine under test are obtained. 

No pulsation or sudden variations must occur in the arma- 
ture current of the driving motor which might vitiate the power 
readings. It is advisable to wire an inductive winding in series 
with the armature of the driving motor in order to steady the 
motor armature current. 



























































































































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f 


O 


























































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-4000 




















































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SOOO 














































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1/ 




























































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s\ 

































































































































































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200 



SOO too SOO 



6O0 



700 



Fig. 58 

SHORT CIRCUIT CORE LOSS ON A 500 KW\, 600 VOLT, 20 POLE 

360 R.P.M., 3-PHASE, 60 CYCLE, A-C. GENERATOR 



In making out reports of core loss the following data regarding 
the machine under test should be recorded on the Testing 
Records in addition to the electrical readings already mentioned: 
viz., circumference of commutator; circumference of shunt and 
series field spools; height of shunt and series field spools; number 
and width of commutator bars; size and material of brushes; 
number of studs and brushes per stud; brush pressure per brush; 
rating of driving motor together with its armature and frame 
number; type and rating and serial number of the machine 
under test. 

On series motors core loss tests should be taken at several 
different speeds covering the range of the speed curve. The 
method used is identical with that described above and will be 
considered in connection with railway and series motor tests. 

126 



Synchronous alternating current machines generally have 
loss measurements taken as outlined above on open-circuit (see 
Calculation Sheet No. 2), and also with the armature of the 
machine under test short-circuited. In the latter case the 
increase in power supplied by the driving motor over that 
required by the friction loss is plotted as ordinates against 
the amperes armature as abscissas, or the open-circuited arma- 
ture voltage due to a given excitation. A curve is obtained 




/O 20 30 40 50 60 70 SO SO /OO //O /20 
Seconcfs 



Fig. 59 

DECELERATION CURVES ON A 3000 KW., 2300 VOLT, 720 R.P.M. 

60 CYCLE, 3-PHASE, A-C. GENERATOR 



similar in character to the open-circuited core loss curve. Such 
test is commonly known as "short-circuited core loss." Fig. 58 
shows the results of such tests after all correction factors have 
been applied. In making this test careful measurements must be 
made of the resistance of the short-circuited armature circuit 
including all leads, before and after the test, since to obtain the 
true short-circuited core loss the PR loss must be subtracted. 
Observations should be made with the short-circuited armature 
current at least 200 per cent of its normal full load value. (See 

127 



Calculation Sheet No. 3.) Care must be taken not to overheat 
the windings. 

Deceleration Core Loss 

It is often necessary to determine the core loss, friction 
and windage losses of large machines when it, is impracticable 
to employ the "belted core loss" method. The "running 
light" reading alone does not allow the separation of the core 
loss from friction and windage. A method known as the 
"deceleration core loss" is used for this purpose. Such tests 



90 
80 
70 
60 

X40 

20 
10 



_L 


t 


/ 


f 


7 




7 


7- 


/ 


/ 


jT 


y 


s^ 


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*" r ~* 







"800 



J200 /600 2000 
Vo/ts /Ir/nati/re 



2400 



Fig. 60 

OPEN CIRCUIT CORE LOSS CURVE FROM 

DECELERATION CURVES IN FIG. 59 



are employed regularly on turbine-driven units, and it is very 
convenient to use them in connection with certain vertical 
waterwheel-driven generators, and other exceptionally large 
horizontal alternators and direct current machines with a 
considerable flywheel capacity. 

A running light reading at normal speed and normal voltage 
should be taken to give the driving power necessary under 
that condition. Where this is not practicable, the moment 
of inertia of the rotating part must be known. This can be 
very accurately calculated for the majority of machines from 
their mechanical dimensions, as given by the working drawings. 

The test is as follows : First drive the machine with no field 
at a little above normal speed, and then suddenly cut off the 
driving power and observe the deceleration, then do the same 

128 



thing with full field on the machine. In the first case the decelera- 
tion is due to the retarding force (friction and windage), in 
the second case due to these factors plus core loss. Readings 
of the speed of the rotating parts should be taken at sufficiently 
frequent intervals to obtain a uniform and reliable curve. 
A set of these curves is shown in Figs. 59 and 60. With the 
aid of these curves together with a "running light" test, or 
a calculation of the kinetic energy of the rotating parts, a 
determination of the value of the core loss, and also of the 
friction and windage, is readily made. The following is a brief 
derivation of the formulae used in calculating such results by 
either method. 

If W = weight. 

r = radius of gyration. 
Si = speed in r.p.m. at time 7\ 
Sa = speed in r.p.m. at time TV 
Wr 2 = flywheel effect. 

Then the kilowatts loss may be found from the following: 

*2308 (S^-Sf) 1 . . . , , .. , o , c. 

— — Wr- - _ = kw. lost in decelerating from Si to S 2 

with any particular field excitation. 

* This formula gives the average power loss from Si to Sz and may be 
derived as follows: 

If M = mass 

v =linear velocity at radius of gyration 
03 = angular velocity 

5 = speed in r.p.m. corresponding to angular velocity 
g =32.2 ft. per sec. per sec. 
£ = kinetic energy at speed 5 and time T 
Ei = kinetic energy at speed Si and time Ti 
Ei = kinetic energy at speed S2 and time Ti 
P = power 

1 W 

The kinetic energy of a moving body at any instant is — Mv 2 . M = — and 

for a rotating body v=ru> and co =— — . 

b(J. 

1 W W / ?7rS\ 2 

Hence E =-- M& = ^-(raj2) =~ I r =^) =0.00017 Wr*S*. 
I Ig Ig \ oU / 

£1 =0.00017 Wr 2 Si 2 (1) 
£•2=0.00017 Wr°- S2 2 (2) 

The energy consumed between Ti and T2=Ei—Ei but for (1) and (2) 
£1 -Ei =0.00017 Wr* (Si 2 -S2 2 ) in foot lb. 
Energy 



Power 



Time 



.-. P=|i-^- 2 = 0.0001 7 Wr* ( ;!f y? ft. lb. per sec. 

/« — il (J2 — i l) 

Multiplying by the proper constants to reduce to kilowatts we have 

kw .0.00017 W,: ^M x^| Xi -^ Wr-- ^=^ which is 
(T2 — T1) 1000 00O 10 10 (T2 — T1) 

the average power loss for speeds from Si to S2. 

(Continued on page 130) 

129 



If T z and T* are respectively the times at which the speeds 
S\ and 52 occur with no excitation on the machine, then in this 

rt. 1 "I 2308 W 2 W-Sf) 

case the loss m kw. = ■ Wr 2 -?= , _ T , 

§The kw. core loss is then the difference between the results 
obtained from the above two formulae. 

With deceleration core loss records the same data must be 
entered upon the record sheets that are required in connection 
with the belted core loss method. Calculation Sheets 2 and 3 
show the standard method of calculating test results, open- 
circuited and short-circuited, taken by the belted core loss 
method. Calculation Sheet 4 shows the method employed in 
calculating results of deceleration core loss, either by using the 
value of Wr 2 , or the running light test. 

Input- Output Test 

It is sometimes required that the efficiency of a machine, or 
motor-generator set be measured by the input-output method. 
The measurement of the power input to the motor or the output 
from the generator is then required. The efficiency of the set 
will then equal 

To find the loss at any particular speed use the following method: 

E =0.00017 Wr 2 S 2 . If ds is the infinitely small change of speed during the 
infinitely short time dt then 

f . "p-moi;™* ) _ . 00034 Wr , s « or a _ KS is 

dt dt dt dt dt 

But — =- is a rate of change of energy or power and -3- =P 
dt dt 

Having obtained a deceleration speed-time curve we can get. P for any 

value of 5. Since -r - is the slope of the curve and can be obtained by drawing 

at 
the tangent to the curve where 5 has the desired value. Substituting values of 

5 and -7- in the above equation gives the value of P. 
dt 

§ If the kw. ' 'running light " has been obtained, 

, .. • r ..,, 2308 _. . (Si* -52*) v WrKSt-Sf) 
kw "running light" =- T7 r- Wr 2 -y= 7F -^- = Ki 



Wr 2 = 



10'° (T2-T1) (T2-T1) 

kw. "running light " (7^2 — Ti) 



also kw. friction = 



Ki(5i2-5 2 2 ) 
KiWr 2 (Si 2 -S2 2 ) 



(Ti-Tz) 
or substituting for Wr 2 

kw friction =7^ =rr Xkw. "running light." 

{Ti— Ta) 

Hence knowing the "running light," the friction can be calculated and the 
core loss separated from the "running light." 

130 



Total output of generator 
total input to motor 
The efficiency of the generator equals 
Total output of generator 
input to motor — motor losses 
The efficiency of the motor equals 

Output of generator +generator losses 
input to motor 

In the case of induction motors, input-output test is some- 
times taken by the string brake method, which is discussed 
in Chapter 12." 

The input-output method of measuring efficiency is one 
of the most difficult tests which the Test Dept. is called upon 
to make, and is subject to considerable inaccuracy. 

This method of the direct measurement of the efficiency of a 
machine should preferably be made by using a duplicate machine 
for power or for load. This is especially true of motor-generator 
sets. The two sets should be wired up for feed back test and the 
electrical losses supplied to the direct current machine, unless 
it is possible to secure a source of alternating current whose 
wave form is identical with that of the alternating current motor 
under test. 

Great care must be exercised in wiring the machines for 
this test. The voltmeters, reading the voltage of the input and 
the output, should be wired as near to their respective machines 
as possible. 

The secondaries of the current transformers should be wired 
directly to the instruments and not through any switches or 
contacts of any kind, and the wiring must be continuous, i.e., 
without an}' splices. The alternating current wattmeters, 
reading the input, must be placed some distance apart. All 
instruments should be carefully tested for stray fields. If the 
machines have series fields, these must be disconnected. 

Before the machine is started the wiring must be thoroughly 
inspected by the Head of the Section or one of his assistants. 
The complete set of instruments, transformers, etc., must be 
specially calibrated before this test is commenced. No reading 
should be taken until the instrument pointers are steady and 
extreme care must be taken to have all readings simultaneous. 
Xo man should read more than two instruments and preferably 
there should be one man for each instrument reading directly 
the input and the output. 

The resulting errors from the input-output method are likely to 
be large, since any inaccuracy in instruments, or personal errors in 
reading, influence the results directly. The errors in reading the 
instruments maybe partially eliminated by taking several readings 
at each load and using the average of all these readings. Even 
with the best conditions for making the input-output test it is 
still much more preferable to ascertain efficiency by measuring 
the losses directly. By adding all the losses to the output at any 

131 



load the input at that load may be obtained, The output 
divided by this result gives the per cent efficiency. The same 
per cent errors in instruments or instrument readings in loss 
measurement test influences the results of the efficiency calcula- 
tions only indirectly; consequently the latter method is superior 
for ordinary testing. 



Shunt F/'e/d 



vvw 



Tora6/ea/?d 
-+- Exc/tat/o/7 



OCo/T?fmi£at/ng/ye/d 
* 'WWW 



Commutat/f?0 
—F/<?/d 




ToExc/tatbn 

Fig. 61 
CONNECTIONS FOR LOAD LOSS TEST 



To Exc Station 



Load Loss Test 

As stated in the section on input-output tests it is much 
more desirable to ascertain the efficiency of a machine by 
measuring the losses directly. However, there are some machines 
which when loaded show a loss which cannot be measured or 
calculated directly from the no-load test. This additional loss 
is known as "load loss." 

To obtain the efficiency of a machine under load without 
making the input-output test, the method of measuring the PR 
loss by means of a booster and observing the input to a separate 
driving motor which supplies the rotation and core losses is used. 
This test requires two similar machines coupled and wired 
together, as shown in Fig. 61. The driving motor should prefer- 
ably be direct connected so as to eliminate the belt loss. 

132 



After the machines have run a sufficient time under load 
to reach constant temperatures they should be shut down and 
the IR drop between the two machines taken at the terminals 
of the machines at currents corresponding to the loads at which 
the load loss is to be observed. These readings will give the 
approximate booster voltages required for the different loads. 

The machines should then be run until the friction is constant. 
Then take several core loss readings on each machine with the 
voltage varying from 75 to 125 per cent of normal. Also take 
careful readings of the input to the driving motor with both 
machines excited to give normal voltage. The difference between 
the motor input (less its own losses) for normal voltage on the 
machines and for friction (less the driving motor losses) is the 
core loss at normal voltage. 

Readings should then be taken at various loads holding the 
voltage on the generator constant at normal, and the booster 
supplying voltage at 10 per cent below the normal drop as 
obtained at standstill; at normal drop; and at 10 per cent above 
normal drop for each load. As the booster and the driving motor 
are furnishing all the losses the sum of the power supplied by 
these two machines should be practically the same for the above 
readings for any given load. This variation in booster voltage 
is made in order to check each point under slightly different 
instrument readings. 

When a complete set of readings is taken the machines should 
be shut down and the IR drop again observed for the various 
currents used in taking the IR drop at the beginning of the test. 
Take the average resistance obtained from the drop at the- 
beginning and at the end of the test and use this for calculating 
the PR to be deducted from the power supplied the two machines 
under the different loads. 

The load loss for two machines will then equal the total 
power supplied by the booster and the driving motor minus the 
PR loss of the circuit minus the PR loss of the driving motor 
armature minus the driving motor input at no-load normal 
voltage on both generators or motors under test. 

As this method gives a fairly accurate measurement of the 
total losses under full load, or at any per cent of full load it is a 
direct method for measuring the load loss and the efficiency. 
However, it requires the most accurate work. The same amount 
of care in the calibration of instruments and transformers, in 
the wiring of the machines and in reading the instruments is 
required as is necessary for the input-output test. The effect 
of brush shift on the load loss is very noticeable. The load loss 
may also be affected by the condition of the brush contact 
surface and by the condition of the commutator. It is, therefore, 
important not to disturb the brushes or commutator after the 
tests have been commenced. 

Maximum Output 

The maximum output of direct current compound wound 
generators is dependent upon their commutation, or heating 

133 



limitations, hence, the maximum output test on these machines 
is usually a commutation test, which will be described later. 
As in shunt wound generators the voltage falls with the load at 
constant field excitation, the maximum output is not always 
limited by commutation. It is not usual to make maximum 
output tests, however, on the above machines, since they 
possess little practical interest. 

In the case of induction motors, the maximum output, or 
breakdown point, is a matter of considerable importance. If 
sufficient power is available, the motor is loaded in successive 
steps, beginning at zero load up to the breakdown point. During 
this test readings of volts armature, amperes armature, speed, 
and motor output are taken and plotted. It is essential that 
the voltage and frequency of the power circuit from which 
the motor is operating be held constant. It is also important 
that readings be taken quickly at overload currents, and that 
the motor be allowed to cool between such readings, or it will 
overheat. Where sufficient power is not available to take a 
breakdown test with normal voltage impressed on the armature 
of the motor, a voltage considerably below normal is used, viz: 
z /i, Y2, or even }/i voltage. It is then necessary to calculate the 
full voltage results from those obtained at the lower voltages. 
This may be done by increasing the power output proportionally 
to the square of the ratio of normal voltage to the lower voltage. 

All maximum output tests on synchronous motors, unless 
stated to the contrary, should be made with a field excitation 
giving minimum input armature current for a given load. 
Readings must, therefore, be taken of volts armature, amperes 
armature, amperes field and volts field with various loads 
from no load to that load which will cause the motor to break 
from synchronisn, adjusting the field strength for each reading 
to give minimum input. The speed of a synchronous motor 
will be constant until the point of breakdown is reached, whereas 
that of an induction motor will decrease from no load to the 
breakdown point. 

In case sufficient power is not available to make a maximum 
output test upon a synchronous motor at its normal rated 
voltage, its voltage may be reduced below normal, as described 
for induction motors. If the minimum input is obtained when 
the readings are taken, the output of the motor at normal 
voltage may be determined in the manner described for induc- 
tion motors. 

The wiring for this test must be arranged so that the arma- 
ture circuit of the motor can be opened immediately when it 
breaks from synchronism. 

Wave Form — Potential Curve Between Brushes 

In the determination of wave form of a d-c. machine the 
following method should be used: The machine should be run 
at normal speed and voltage. A pair of voltmeter leads separated 
a distance equal to the width of one commutator bar is placed 
on the commutator under the center of one pole and moved from 

134 



bar to bar over to the center of the next pole of like polarity, 
the voltage being read at each step. In this way the voltage 
between bars is obtained for a complete cycle of 360 electrical 
degrees. 

The readings should be corrected and plotted as ordinates 
against the number of the corresponding bars as abscissae and 
a sketch showing the position of the poles should be made on 
the same sheet in conjunction with the curve obtained. 

Wave form on alternators is obtained by the use of the 
oscillograph. 

Over-Speed Test 

Very often the Testing Department is called upon to take 
tests on a machine with the revolving part running at a specified 
speed above normal to test for mechanical strength. 

On all large machines this test is always taken with the rotor 
placed in a large pit and driven mechanically at the designated 
speed. Careful measurements are taken by the Mechanical 
Inspectors of definite parts of the rotor under test and the test 
then started. The machine should be shut down and check 
measurements taken at normal speed and at 22, 41, 58, 73, and 
87 per cent over normal to see that there is no stretching of the 
metal or loosening of the different parts. 

Xo over-speed test should be started unless an especially 
appointed man is present to witness the test. 

Small machines are usually run inside the building after being 
covered with heavy castings as a precaution against accident. 



135 



CHAPTER 7 

DIRECT CURRENT GENERATORS 

The tests on direct current generators may be divided as 
follows: Preliminary tests; short commercial and adjustment; 
heating tests; special tests; input-output tests; over speed 
test; and wave form. 

Preliminary tests consist of drop on spools; polarity; cold 
resistance measure; air gap; checking of armature and field 
specifications; brush and equalizer spacing; brush alignment; 
commutating pole spacing; and preliminary inspection, all of 
which have been explained in preceding chapters with the excep- 
tion of equalizer spacing. 

Equalizers consist of rings or cross connections tapping into 
equi-potential points on the winding of multiple wound arma- 
tures between each pair of poles. These rings prevent inequali- 
ties in voltage between brushes of equal potential due to 
inaccurate centering of the armature. They allow alternating 
current to flow from the stronger to the weaker pole pieces, which 
slightly demagnetizes the former and magnetizes the latter, thus 
equalizing the voltage at the brushes. Not only do these rings 
prevent an interchange of heavy cross-currents between brushes 
but they also compensate for inequalities at the pole pieces 
tending to bend the shaft or overheat the bearings. These rings 
must be examined carefully to see that the taps are equally 
spaced and that the connections are tight. 

General Instructions 

After checking up all of the above points the machine should 
be turned over slowly and the eccentricity of the commutator 
carefully measured. If it is eccentric more than 0.005 in. it must 
be trued according to the method given in Chapter 3, page 95. 

The man in charge of the machine should obtain the sheet 
of Testing Instructions from the Head of Section. The machine 
should be wired according to the correct wiring diagram obtained 
from the Head of Section who should then see that the wiring 
is inspected and checked. The different methods for obtaining 
load are described in subsequent pages. 

It is absolutely necessary that the machine operate correctly 
when connected according to this print, and any discrepancy in 
operation should immediately be referred to the Head of Section. 

Make provision for reading volts and amperes line, volts 
and amperes field, and speed. 

Using the precautions mentioned in Chapter 4, page 100, the 
machine may then be started. The brushes should first be set 
on the mechanical neutral by the Head or Assistant Head of 
Section, by shifting the brush-holder yoke until the brushes 
are in line with the center of the pole pieces. This position can 
be located accurately enough by sight on machines without 
commutating poles. On commutating pole machines a more 
accurate method is used which is described later. 

136 



If the machine has been assembled and connected correctly 
it should "build up" when the shunt field switch is closed and all 
resistance is cut out. To make sure that all the resistance 
has been cut out of the field circuit, the field boxes may be short- 
circuited by a short piece of wire temporarily held against the 
terminals. If it does not build up, the connections should again 
be checked with the wiring diagram and the polarity and resist- 
ance of the shunt field, and the different specifications re-checked. 
If these prove to be correct, the field switch should be opened 
and the residual armature voltage noted. If, upon again closing 
the switch, this decreases or drops to zero, it shows that the 
machine is not wired properly and that the current tends to flow 
in the wrong direction through the field. This condition should 
be referred to the office, as the only way to remedy it would be to 
change the connections. If, however, upon closing the field 
switch the residual armature volts do not diminish it may be 
necessary to "flash the field" by sending a current through it 
in the proper direction from some external source. 

The building up of a series generator is a more complicated 
operation. The load increases with the voltage and great care 
must, therefore, be taken in obtaining the correct external 
resistance to prevent the voltage from increasing rapidly. As it is 
practically impossible to decrease the external resistance enough 
(i.e., put the blade of the water box in far enough) to allow 
the generator to pick up, the usual method is to put the water 
box blades in and short-circuit one of the boxes with a fuse 
wire, then close the circuit breaker and switches. If the machine 
then starts to pick up, and the voltage decreases as soon as 
the fuse wire burns away there is too much resistance in the 
water boxes. They should, therefore, be salted (to decrease 
the resistance) and the operation repeated. Should the resist- 
ance in the boxes be too low the load will increase very rapidly 
and the breakers may have to be opened to prevent the machine 
arcing over between brushes. 

MACHINES WITHOUT COMMUTATING POLES 

SHUNT ADJUSTMENT 

After the machine builds up in the proper manner a saturation 
curve should be taken as described in Chapter 6, page 120. 

The machine should then be compounded according to the 
Testing Instruction sheet. This test is very important and the 
results must be passed by the Head, or Assistant Head of 
Section. The machine must first be adjusted for good com- 
mutation. No fixed rules can be laid down for judging com- 
mutation, but Fig. 62 shows a chart covering the various grades 
of commutation and should serve as a guide in judging this 
question. The machine should be loaded by one of the methods 
described under "Actual Load Test" described later. 

In order to obtain good commutation on generators without 
commutating poles, it is necessary to shift the brushes from 
the mechanical neutral in the direction of rotation to a position 

137 



that will give satisfactory commutation at both no load [and full 
load. It is not usually possible to obtain sparkless (No. 1) 
commutation on generators without commutating poles, but 
it should not be worse than No. 2, as shown in Fig. 62. If it is 
impossible to obtain satisfactory commutation by shifting the 
brushes, the matter should immediately be reported to the Head 
of Section. 

After satisfactory commutation has been obtained the posi- 
tion of the brush-holder yoke should be marked with a chisel 
and the machine then given a cold compounding test as follows: 



A/OJ 



A/o./i 




L 



A/oJg 



No.2 





No .3- 



No.4 




c 



Fig. 62 
VARIOUS DEGREES OF GENERATOR AND MOTOR SPARKING 



The voltage should be adjusted at no load with a falling field, 
that is, the voltage should be brought considerably above 
normal and gradually reduced to normal by "cutting in" the 
field rheostat. Then without changing the position of the field 
rheostat normal load should be put on the machine with the 
speed held constant and a reading taken at full series field 
of volts armature, amperes, volts and amperes field and speed. 
The volts armature should rise considerably above the rated 
full load voltage of the machine. If it does not rise but falls, 
the series field is either weak or reversed. If the whole series 
field opposes the shunt field it may be easily checked by tracing 

138 



out the direction of the current after it leaves the armature. 
All field spools are wound in the same direction so that only 
the general direction around the frame need be traced. 

The series field may be wound in an opposite direction to 
the shunt field. To test this, reverse the series field leads. 
Should the machine over-compound with the series field in the 
reversed direction from the shunt field, the test should 
immediately be discontinued until the spools are changed. A 
report of this defect should be made to the Head of Section. 







^-^ 


^^ 


.4? 


^<^ 


*zs -T 


-**4 


JZ* 


S7 


sy 


/_/ 


/_/ 


/Z? 


s_7 


/-£ 


y / 




/ / 


7 7 


Z 7 


1 _r 


_/ 7 


t J 


t^ 

* 


% 


_i 


/ Futtload 



^Amperes Mac/?//?e 

Fig. 63 
SERIES CHARACTERISTIC 

It may be that only a part of the series field is reversed. 
In locating a reversed series spool it is best to excite the series 
field up to 20 per cent of full load current, then either try for 
polarity or take a potential curve using the series field as a 
source of excitation. Extremely low voltage will appear on the 
potential curve, both in front of and behind the reversed spool. 

If the machine overcompounds correctlv, a shunt should be 
placed on the series field and adjusted until the specified com- 

139 



pounding is obtained. The no-load point should be taken with a 
falling field as above, then, without touching the field rheostat 
the load should be applied gradually until full load is reached. 
A reading should then be taken as above. This process should be 
repeated until the shunt has been so adjusted that a full load 
voltage is obtained about one per cent above that specified. 
This will allow for voltage drop in the armature due to heating. 
The shunts for the series field are usually made up of cast iron 
grids as specified in the Engineering Notice. 

Machines that are for direct connection to steam engines, 
etc., should have allowance made for the drop in speed from no 
load to full load, due to engine regulation. 

The shifting of brushes on series generators necessitates 
good judgment. The brushes should first be given a little 
more lead with full load than is necessary for commutation. 
The load should then be gradually reduced, and the commutation 
noted until zero voltage is obtained. Should sparking occur 
at any point, a readjustment of the brushes should be made by 
shifting them back towards the neutral point, provided that 
full load commutation will so allow. 

A series characteristic is taken on all series wound generators. 
This is done by increasing the load by small steps until full 
load is obtained, amperes line and volts machine being recorded 
at each step. The load is then reduced by small steps to no 
load, the same readings being taken. A curve is then plotted 
between amperes as abscissae and volts machine as ordinates. 
See Fig. 63. 

In the case of series machines forming part of booster sets, 
the guarantee sometimes does not allow this curve to deviate 
by more than a certain percentage from a straight line. The 
curve should be taken in all cases with the German Silver shunt 
in place, if the latter is necessary. 

HEATING TESTS 

Two methods may be used for making heating tests, i.e., 
Actual Load Tests and Equivalent Load Tests. 

ACTUAL LOAD TEST 

Several different means for obtaining actual load test may be 
employed, such as the "water box," "feeding back" and 
"circulating current" methods. 

Water Box Method 

The "water box" method familiarly known as the "dead 
load" method, as its name implies, consists in driving the 
machine by a motor or other means and loading it directly upon 
a water box. See Fig. 64. This method entails considerable 
expense, since all the power generated is lost. On large machines 
requiring a considerable amount of power to be dissipated, 
several water boxes are connected in multiple. The standard 
water box used in the Testing Department is designed to 

140 



dissipate 75 kw. continuously and care should be taken to 
have the circulating water in the water boxes so adjusted that 
violent boiling will not occur, as it is difficult to hold the load 
constant when this occurs. The load should be evenly divided 
between the different water boxes. 



_R&/si4fkrf 







f^S-Resfctance 



Sfr/fj/7f/d 



%5/?unt ® \V7/ 



&5/?unt 
ffekt 



-^-a 



water 

&0X 



Fig. 64 
CONNECTIONS FOR LOADING D-C. GENERATOR ON A WATER BOX 

Feeding Back Methods 

To obviate the loss of power and reduce the cost of testing 
the "feeding back" method is used when possible, especially 
with large d-c. machines or motor-generator sets. In this 
method the total machine losses are supplied either mechanically 
or electricallv from an external source. 




Fig. 65 
CONNECTIONS FOR MECHANICAL LOSS SUPPLY FEED BACK 



In the mechanical loss supply method, two machines of the 
same size and voltage should be belted or direct connected 
together and mechanically driven by a motor large enough to 
carry the losses of the set. Connections are made as in Fig. 65. 
If the machines have series fields the one to operate as a motor 
should be so connected that it will run as an accumulative 
compound wound motor. The voltage of each machine should be 
brought up as in a generator and the machines thrown together 

141 



by closing the switch between them when the voltage across it is 
zero. One machine is then adjusted to act as a motor by weaken- 
ing its field. This lowers its generated voltage and causes current 
to flow through the machines which should be adjusted to the 
required value. The speed is held constant by the loss supply 
motor. After running at the proper load for the specified time, 
the heat run should be taken off and tests finished according to 
the standard requirements. 

In the method of electrical loss supply, two machines are 
direct-connected or belted together, and the losses supplied 
electrically. See Fig. 66. The machine acting as a generator 
should be run under normal operating conditions of voltage 
and current. The speed is held by varying the field of the motor. 
It may be necessary to connect the motor field in series-multiple 
to obtain the required condition. 



7&WFJ? 



.c 



yssr Jjr^L 




Shunt 
FFeM 



Fig. 66 
CONNECTIONS FOR ELECTRICAL LOSS SUPPLY FEED BACK 



When Compound Wound Generators are being tested by 
this method the series field of the motor must be included or 
the load will be unstable. 

Another method of "Feeding Back," often used, is to run 
the entire .load back on the main supply circuit from which 
the motor is run which drives the generator in test. If the 
main supply circuit is likely to vary in voltage, it may be neces- 
sary to insert resistances between the generator and supply. 
It sometimes happens that the no-load voltage of the generator 
is below that of the supply. As changing the line resistances 
will have no effect at no-load, the generator voltage must be 
increased until it is equal to that of the main supply circuit. 
Having previously calculated the full-load field current from 
the no-load current, and the ratio of compounding voltages, 
the machines are thrown together and full load put on the 
generator by cutting out the variable resistance. 

Two similar motor-generator sets can be tested very readily 
by the "Feeding Back" method. 

142 



As an illustration, suppose each set consists of an induction 
motor and a d-c. generator. In this case, connections are made 
as in Fig. 67. The a-c. and d-c. ends of the respective sets 
are connected together, one set being run normally and the 
other inverted. The induction generator feeds back on the 
induction motor, both taking their exciting current from the 
alternator (A) which supplies the losses. They are started 
one at a time from the a-c. end, and the d-c. ends adjusted 
by means of a voltmeter across switch (P). The d-c. motor 
field is weakened until the ammeter in the d-c. line indicates 
that normal current is flowing. The weakening of the motor 
field allows the speed of the inverted set to increase just enough 
to load the induction generator while it also decreases the 
counter e.m.f. of the motor a sufficient amount to allow full 
load current to flow in the d-c. circuit. This load must be 




Fig. 67 
CONNECTIONS FOR INDUCTION MOTOR-GENERATOR SET FEED BACK 



closely watched as it is unstable. Load instability is a rather 
common occurrence in "Feeding Back," due either to variations 
in shop voltage or speed. 

Circulating Current Method 

It will be noted in the "Feeding Back" tests described 
that it is necessary to weaken or strengthen one of the fields to 
obtain the load. To conduct the test with the same field excita- 
tion on both machines the armature of a separately excited 
booster may be connected in series with the armatures of the 
two machines being tested. The machines, connected so that 
they run at the same speed, are brought up to normal speed 
by means of the motor supplying the losses. The connecting 
switch is then closed and the booster field strengthened until 
normal current flows in the armature circuit, the field current 
being adjusted to give the same excitation on both fields. The 
voltage is held across the motor terminals by varying the speed 
of the loss supply motor. 

143 



EQUIVALENT LOAD TEST 

Very often it is found impossible to run actual load tests, 
especially on large machines on account of limited facilities. 
Equivalent load tests have consequently been devised in which 
the heating of a machine at a certain load may be closely 
ascertained without actually loading it. 

A direct current machine may be satisfactorily tested in this 
manner by short-circuiting the armature upon itself or through 
the series field connected so that it will not build up as a series 
generator. The shunt field is separately excited from an external 
source until the required current flows through the armature, or 
armature and series field. This method is the one usually used 
for baking and settling the commutator. Amperes armature 
and field, and volts field should be read throughout the run. 
When this test is run for a commutator bake, the final tem- 
perature of the commutator should be recorded. 

A similar method of making an equivalent load run consists 
in running the generator under reduced kilowatt output by 
lowering the voltage and keeping the current normal. In this 
case the fields are all wired in and all readings taken as during 
a full load run. 

NORMAL LOAD HEAT RUN 

After the machine has been properly compounded the heat 
run may be started. Before going ahead with this test, the 
tester should read carefully all the instructions contained in 
Chapter 4, regarding the location of thermometers and reading 
of temperature, etc. 

In addition, the brushes and commutator should be in first 
class condition and under no circumstances should a heat run 
be started until the brushes have at least a 90 per cent fit. The 
brushes should be carefully watched to see if they pick up 
copper, and if such is the case the commutator while running 
should be cleaned with a piece of canvas and the copper wiped 
off the brushes. This should be repeated until the trouble is 
entirely eliminated and the commutator shows a tendency to 
take on a smooth surface. No heat run should be started if the 
commutator tends to become gummy, as satisfactory commuta- 
tion cannot be maintained for any length of time. 

During the heat run all conditions should remain normal and 
the line current, voltage and speed be held as specified on the 
testing instructions. Amperes and volts field should be read. 
Readings of all instruments and thermometers should be taken 
and recorded every half hour. Commutation should be noted 
and recorded at every reading during the run. The amperes 
field should increase slightly during the run and the volts field 
should increase an amount corresponding to the higher tem- 
perature of the field coils. When the machine reaches constant 
temperature, as shown by thermometers, it should be shut 
down and final temperatures taken of all parts and the hot 
resistances of the various circuits carefully measured. The rise 

144 



of temperature by the rise in resistance should be calculated 
by the formula given on page 112. 

OVERLOAD HEAT RUN 

All overload heat runs require considerable attention. The 
machine should first be brought to normal load temperatures 
before the overload is applied. The overload should be carried 
only for the specified time, since in many cases the temperature 
rises rapidly throughout the whole period of the run; hence 
lengthening or shortening this period a few minutes may cause 
several degrees difference in the final temperatures obtained. 
As a general rule, readings of all instruments and thermometers 
should be taken every fifteen minutes. If the voltage should 
fall below the rated full load value with normal field, it should 
be raised to and kept at the rated amount during the run. The 
amperes and volts field will increase during the duration of the 
overload. 

MISCELLANEOUS TESTS 

High Potential Test 

After the necessary heat runs and while the machine is still 
warm the wiring should be removed and the high potential test 
applied. 

Compounding Curve 

After the heat runs have been taken and final temperatures 
recorded, a hot compounding curve should be taken. The hot 
compounding test is similar to the cold compounding test 
described on page 138, except that the compounding must be 
adjusted very close to the value specified on the testing instruc- 
tions. When this has been done a complete curve should be 
obtained with readings taken in the following order: No load, 
full load, 3 i load, H load, 34 load, no-load, and 125 per cent load. 
The field rheostat must not be moved from the position for the 
no-load setting. A curve should be drawn with load as abscissae 
and volts armature as ordinates. 

Rheostat Data 

After the heat runs, rheostat data should be taken in the 
same manner as saturation, with the exception that the brushes 
are placed at the running position instead of the neutral point. 

On machines which do not require heat runs, only two points 
need be taken on the curve, namely, at full voltage and half 
voltage. 

Shunt Regulation 

Shunt regulation should be taken on shunt wound generators 
when requested by the Engineers. A reading should be taken 
first at no-load normal voltage. Without changing the rheostat, 
l /i load should be thrown on and a reading taken of amperes 

145 



armature, volts armature, amperes field and volts field. Holding 
34 load, the voltage should be brought up to normal and the 
same readings taken. The load should now be increased to Yi 
full load, with the rheostat in the same position, similar readings 
being repeated. This test is repeated for z /i and full load. With 
full load on the machine the voltage should then be brought up 
to normal. With the field rheostat in this position the load is 
then taken off the machine and the rise in voltage observed. 
All these entries should be made on the Record Sheet. A curve 
should be plotted with amperes armature as abscissae and volts 
as ordinates. See Fig. 68 and Calculation Sheet 28. 

If the voltage should drop to zero when 34 load is put on 
the machine, the load should be applied in smaller increments. 
Speed should always be kept constant throughout the test. 




300 400 SOO 

/7/7?peres Line 



Fig. 68 

SHUNT REGULATION CURVE ON A 6-POLE, 100 KW., 

600 R.P.M., 125 VOLT GENERATOR 



Running Light 

Running light readings should be taken before the machine 
is stripped out. This test is described in Chapter 6, page 122. 

Field Compounding 

Field compounding is taken when called for by the Engineers. 
From its results is obtained the additional ampere turns field 
necessary to overcome armature reaction and IR drop in the 
machine from no-load to full load. The test is made by sepa- 
rately exciting the field of the machine under test, in order to 
hold the voltage at its terminals constant as the load is increased 
from no load to full load. Readings of amperes field, volts 
field, amperes armature, volts armature and speed are taken at 
no load and at least three intermediate points between no 
load and rated load. It is generally required, and usually 
advisable, to take an observation at 25 per cent overload, 
if the power is available. All readings should be made with 
a rising field current. Fig. 69 shows a curve of field compounding 
in which is plotted amperes field or ampere-turns field as ordi- 

146 



nates, and amperes armature as abscissae. See also Calculation 
Sheet Xo. 5. 

Stud Potential Curve 

This test is sometimes taken on machines equipped with 
multiple wound armatures which are not furnished with equalizer 
rings and is obtained as follows: 

All the brushes except those on two adjacent studs are 
raised from the commutator, the voltage is then raised to 
normal and the field current noted. This field current and the 
speed must be held constant for all other points on the curve. 
The brushes on stud No. 3 should now be lowered, those on 
Xo. 1 raised and the voltage read between studs No. 2 and 
Xo. 3. This should be continued until voltage readings have 
been taken between each pair of studs. The test should be 



r 

r 



/oo 



200 



SOO <400 soo 

Amperes /Ir/natt/re 



eoo 



Fig. 69 

FIELD COMPOUNDING CURVE ON A 150 KW., 250 VOLT, 225 R.P.M. 

6 POLE D-C. GENERATOR (6 BAR BRUSH SHIFT) 



made with the field current rising. The maximum voltage 
variation permissible is 4 per cent of the average value. This 
test, although similar in name, should not be confused with 
the bar to bar potential curve taken to determine the wave 
form of a d-c. machine and described in Chapter 6. 

SPECIAL TESTS consist of saturation and core loss, shunt 
adjustment, compounding and commutation tests. These have 
all been previously described. 

INPUT-OUTPUT TEST, OVER-SPEED TEST, and WAVE FORM 
have been described in Chapter 6. 

COMPLETE TEST consists of normal and overload heat runs, 
saturation and core loss, compounding and commutation tests. 

STANDARD EFFICIENCY TEST is made by the method of losses. 
Page 430 and Calculation Sheet 11 give the method for calculat- 
ing the efficiency of a d-c. generator. See Fig. 70. 

THREE-WIRE GENERATORS 

Some direct current generators are provided with collector 
rings for operation on Edison three-wire circuits. The series 
field is usually divided and one-half placed on each side of the 

147 



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EFFICIENCY AND LOSSES ON A 100 KW., 6 POLE, 275 R.P.M. 

525/575 VOLTS, COMPOUND WOUND D-C. GENERATOR 



148 



armature, as shown in Fig. 71. Tests are made as on other d-c. 
generators with the following additional special points: 

In compounding a machine, care should be taken to have 
the shunts in each half of the series field of approximately the 
same size, and when the correct compounding has been obtained 
"shunt balance readings" should be taken as follows: 

Remove the shunt from one side of the series field and take 
readings at no load and full load. Replace this shunt and repeat 
the readings for the other half of the series field. The line voltage 
obtained on these two readings should check. 



-vV\AAA/W 



Shunt 
Ffrkt 







Fig. 71 
THREE- WIRE GENERATOR 

Unbalanced Readings 

If unbalanced readings are required, a compensator should 
be wired as in Fig. 71. A reading should be taken at no load 
normal voltage. With no change in the field and holding con- 
stant speed, \i load should then be thrown on one side of the line 
and the voltage read from the neutral to each side of the line. 
Volts and amperes line, volts and amperes field should also be 
read. One-quarter load should then be put on the other side of 
the line, giving a balanced load, readings being taken as before. 
The load should then be increased to 3^ load on one side, this 
procedure being continued until 125 per cent balanced load is 
obtained and readings taken at each step. Instructions some- 
times call for 50 per cent unbalancing, in which case the load is 
increased 50 per cent at each step instead of 25 per cent. 

Revolving Compensator 

One type of three-wire generator has its compensator 
mounted directly on the shaft at the back of the armature and 
is equipped with only one slip ring. 



COMMUTATING POLE GENERATORS 

General Notes 

The general instructions covering mechanical inspection, 
measurement of air gaps, drop on spools, etc., applying to all 
other generators must be followed in testing machines with 

149 



commutating poles. The function of the commutating pole is 
to improve commutation and in testing, commutation is, there- 
fore, important. The pole spacing should check within -^ in. 
as specified on page 82. 

The commutating poles produce the necessary flux for 
neutralizing the effect of armature reaction. This flux prevents 
the shifting of the neutral point between no load and full 
load which occurs in d-c. machines not equipped with them. 
In addition it aids the current reversal in the armature coils at 
commutation. To obtain the proper reversal without sparking 
at normal current requires a definite number of ampere turns 
in the commutating field.. The brushes are placed on the 
mechanical neutral, and if the machine is properly com- 
pensated the mechanical neutral will check with the electrical 
neutral. 

Baking Commutators 

Commutators of commutating pole machines are baked 
according to the method on page 144. The brushes must never 
be shifted under load, so as to produce sparking and heating. 
They must always be shifted at no-load to insure their not 
being set beyond the safe limit of no-load commutation, thus 
rendering it possible for the machine to flash over if the load is 
suddenly removed. In all cases, the Head of Section or his 
assistant must be consulted before the brushes on any com- 
mutating pole machine are shifted far from the neutral. 
It must also be remembered that the armature must not be 
short-circuited through the commutating pole winding when 
baking a commutator, as in this case the majority of machines 
will build up as series generators, and the armature current can- 
not be controlled. 

Locating the Neutral 

Referring to Fig. 72, one armature coil contained in a pair of 
slots in the armature core and the corresponding commutator 
segments are marked for the convenience of the Testing Depart- 
ment. The coils are marked with red paint, and the ends of the 
corresponding commutator bars are stamped with the letter " O. " 
In a machine with full pitch winding the two red marked arma- 
ture conductors (A) forming a coil will come one pole arc apart, 
and in setting the brushes these conductors should be placed 
directly under the centers of the commutating poles as shown, 
and the brushes shifted until the center of the brush rests on the 
center line of the commutator segment corresponding. On a 
fractional pitch winding the two red conductors will not span a 
full pole arc, and hence they should be so located that they are 
equi-distant from the center of their respective" poles as shown by 
the dotted lines B-B, and the brushes set as above. If there is 
more than one coil per slot, there will be a corresponding num- 
ber of commutator segments stamped O-O, but the middle one 
should be used. After the brushes are set the usual tests for 
building up, saturation, etc., may be continued. 

150 



Shunt Adjustment 

It is the aim of the Engineers to design the commutating 
field so that it will operate without a shunt; however, it is some- 
times necessary to shunt out some of the current to obtain the 
proper compensation for satisfactory commutation. A thorough 
trial should be made, however, with full commutating field. In 
adjusting for commutation, a compound wound machine may be 




Fig. 72 
DIAGRAM SHOWING MARKING OF ARMATURE AND 
COMMUTATOR FOR LOCATING MECHANICAL 
NEUTRAL 



run with full series field. If the commutation is not satis- 
factory at full commutating field about ten per cent of full load 
current should be shunted. If the commutation is improved 
more current should be shunted until sparkless commutation 
(Xo. 1, see Fig. 62) is obtained at all loads up to fifty per cent 
overload unless otherwise specified. 

If the commutation is not improved by shunting current 
the Head of Section should be notified. Sometimes a slightly 
better effect is obtained by shifting the brushes forward or 
backward from the neutral point. This, however, should only 

151 



be done after all other adjustments have failed, and permission 
has been obtained from the Head of Section. 

If none of these methods gives satisfactory results the 
trouble may be due to a weak field. This can be ascertained by 
separately exciting the commutating field and sending a larger 
current through it than would otherwise be obtained with 
normal load on the machine. If such procedure improves the 
commutation the fact must be referred to the Engineers to have 
changes made. 

The iron grid shunts used on the larger machines should 
be placed so that the edges of the grids are in a vertical position 
and as near as possible to the position they are to occupy when 
in actual operation. Care should be taken to see that they 
contain ample current carrying capacity and do not heat up. 
If they are allowed to heat excessively the amount of current 
shunted changes, and thus destroys the commutation of the 
machine. 

When the final brush position has been determined it should 
be marked with a chisel. On the larger machines a trammel 
should be made by the shop to assist the customer to assemble 
the brushes in a correct position. This trammel consists of a 
steel bar pointed on the ends and of the correct length to mark 
the distance from two points in the magnet frame to the point 
on the commutator on which the brushes on one stud should be 
placed. 

After the proper adjustment has been obtained an ammeter 
should be wired in and the amount of current shunted carefully 
measured. 

Inductive Shunt 

Any condition which would suddenly under-excite the corn- 
mutating field or make it inactive would make the machine 
sensitive and cause bad sparking at the brushes. If the corn- 
mutating field is equipped with a grid or German Silver shunt 
and the machine becomes short-circuited, the inductance of the 
commutating field forces the instantaneous heavy overload 
current through the non-inductive shunt and leaves the com- 
mutating field without sufficient excitation to neutralize the 
armature reaction. The electrical neutral immediately shifts 
and bad commutation results. 

To eliminate this trouble an inductive shunt is sometimes 
used across the terminals of the commutating field in series with 
the non-inductive shunt. This shunt will be used only when 
called for by the Engineers, but when so specified it should be 
in circuit while the commutating field is being adjusted for com- 
mutation. The inductive shunt is of low resistance, and is de- 
signed to have an inductance greater than the commutating field. 

If the machine has an inductive _ shunt and flashing or 
violent sparking is produced by throwing a heavy load on and 
off quickly, try adjusting the air gap of the inductive shunt. 
With a given winding on the core, the inductance of the shunt 
may be varied by changing the air gap and the relative induc- 

152 



tance of the shunt and commutating winding be thus altered. 
If the current read on the meter in the shunted circuit quickly 
falls to zero when a heavy load is thrown off by tripping a 
breaker, and the brushes show sparking, there is too little 
inductance in the shunt and its air gap should be decreased. 
The air gap should be adjusted so as to give minimum sparking 
when the machine is operating with a highly fluctuating load. 

Motor Operation 

Some machines are required to run as motors as well as 
generators. When such operation is specified they are equipped 
with a switch for reversing the series field, so that they may run 
as accumulative compound wound motors. Such machines 
should be tried under load as motors and have shunts adjusted 
as specified above. If possible the same shunt should be used 
for motor operation as was obtained when the machine was 
operating as a generator. In no case should a machine be 
passed for both motor and generator operation unless it will 
operate satisfactorily under both conditions without changing 
the brush position. 

Compounding, Etc. 

After satisfactory commutation has been obtained the 
machine should be compounded and other tests taken as des- 
cribed for generators without commutating poles. 

THREE-WIRE COMMUTATING POLE GENERATORS 

Commutating pole machines equipped for three-wire oper- 
ation should be adjusted similarly to the above. Care must 
be taken to see that the shunts on each half of the commutating 
field are approximately equal. 

EXCITERS 

Exciters are tested in the same manner as other direct cur- 
rent generators, as previously explained. All 125 volt exciters 
must give at least 175 volts with full shunt field at no load. 
Most 125 volt compound wound exciters are compounded at 
both the rated voltage and at 80 volts. On small exciters the 
brushes are usually shifted ahead of the neutral point to obtain 
the compound at 125 volts and a shunt placed across the series 
field for the 80 volt condition. The latter is only an approxi- 
mate setting and no attempt is made to get extremely accurate 
results. 

Stability Test 

Direct connected exciters should be given a Stability Test. 
With rated no-load voltage on the alternators, raise and lower 
the speed 2 per cent above and below normal, noting and 
recording the voltage change in each case. The change in 
voltage should not exceed 6 per cent of normal no-load voltage 
in either case. The no-load voltage setting should always be 
made with a rising field. 

153 



THREE- WIRE BALANCER SETS 

In the operation of three-wire circuits the load often tends 
to become heavier on one side than the other with a consequent 
unbalancing of the voltage. To obviate this, small motor- 
generator sets called "balancer sets" are used. 

In its most common form the balancer set. consists of two 
similar machines on one shaft or with their shafts coupled 
together and their armatures connected in series across the out- 
side mains. Each machine is wound for one-half the voltage 
between the outside mains, and their combined rating in amperes 
is made equal to the probable difference in load between the two 
sides of the system. This unbalanced load is carried by the 
neutral wire taken from the balancer at the point where the 
two armatures are connected. 

When the load on the system is balanced, the two machines 
run as motors in series across the outside lines, no work is done, 
and the only current used is that necessary to overcome the 
losses of the machines running free. As soon as one side of the 
system becomes more heavily loaded than the other, the drop in 
voltage on this side will be the greater and the voltage impressed 
on the machine on this side reduced. The other machine, 
having the higher voltage, will tend to run faster than the first 
and drive it as a generator. The machine operating as a motor 
will act as a load on its side of the system, lowering the voltage 
on that side, while the generator will supply current to and raise 
the voltage on the heavily loaded side. The combined current 
of the two machines equals the unbalanced load of the system 
and the total effect is to restore the voltage balance of the system. 
As the unbalanced load on the system may shift from one side 
to the other, this action of the balancer must also shift. Either 
machine may at any instant be operating as a motor and the next 
instant as a generator. As the direction of rotation is always 
the same it is impossible to tell, without knowing how the load is 
balanced, which is the motor and which the generator. 

Balancer sets are adjusted by loading one side at a time with 
the required current in the neutral wire. 

Fig. 73 shows the connections for a compound wound, corn- 
mutating pole balancer set connected for loading in the Testing 
Department. These sets may be shunt wound, shunt wound with 
commutating poles, or compound wound with commutating poles. 

Balancer sets should receive the same preliminary inspection 
and tests as d-c. generators and motors, and after being wired 
according to the correct diagram, should be adjusted for com- 
mutation, field balance, speed and compounding. 

Commercial and Adjustment test consists of balancing tests 
and the operation of the set to demonstrate that it is a duplicate 
electrically of machines of the same type already shipped and 
that it is free from manufacturing defects. 

Balancing tests consist of adjusting both machines of the set 
so that the voltage across each machine shall always be balanced 
within 2 per cent. The sum of the two voltages will be equal 
to the applied voltage. The wiring on balancer sets must be 

154 



done as carefully as that for motors as either end of the set may 
be operating at any time as a motor. The same precautions, 
therefore, must be exercised as when operating a motor. 






for/ob/e rT&s/s to/ice 



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Fig. 73 
WIRING DIAGRAM FOR TESTING BALANCER SET 



VL = Impressed volts line 
VA, VAi = Volts machine A and Ai 
VF, VFi = Volts shunt field A and Ai 
AL = Amperes line 



AA, AAi = Amperes armature A and Ai 
AF, AFi = Amperes shunt field Aand Ai 
AN = Amperes neutral 



Shunt Wound Sets 

On shunt wound sets the fields are cross connected and should 
be adjusted and the brushes shifted to such a position that the 
proper voltage balance is obtained. One side of the set is 
loaded at a time as shown in the figure. Satisfactory com- 
mutation and speed must also be obtained, and when such condi- 
tion has been established with one side running as a generator. 

155 



the set should be reversed and the other side adjusted to cor- 
respond. When both sides have been properly adjusted the 
set should operate with either end running as a motor. 

Shunt Wound Sets with Commutating Poles 

If the set is equipped with commutating poles, it should be 
adjusted with the brushes placed on the mechanical neutral 
as on other commutating pole machines. After good com- 
mutation has been obtained (by adjusting a shunt in the com- 
mutating field, if necessary), the proper voltage balance should 
be obtained. It should not be necessary to shift the brushes from 
the mechanical neutral, but if a balanced condition cannot other- 
wise be obtained the Head of Section should be notified im- 
mediately. 

Compound Wound Sets with Commutating Poles 

On these sets, the commutating field should be adjusted for 
commutation and the shunt and series fields adjusted for the 
proper voltage balance, after satisfactory commutation has 
been obtained. It should be noted that on a compound wound 
balancer set the machine operating as a motor runs as a dif- 
ferentially wound machine while the other acts as an accumula- 
tive compound wound generator. Therefore, care should be 
taken in adjustment as the set may have enough series field to 
cause it to speed up to a dangerous point. 

HEAT RUNS, ETC. 

After the set has been adjusted the heat runs should be 
taken by loading one side for the specified time with the required 
current flowing through the neutral wire. All readings of voltage 
and current should be carefully checked to see that they are 
consistent. 

Saturation may be taken by operating each machine as an 
individual generator. 

Core loss may be taken on a set with three or more bearings 
by the method of belted core loss previously described, the belt 
being run over the coupling between the machines. 

On two bearing sets the core loss is obtained by a series of 
"running light" readings on each machine as follows: 

With one end operating as a shunt motor read the input 
with no voltage on the other (a) with brushes down, (b) with 
brushes up; then (c) with normal voltage on the generator end 
with brushes down. These readings should then be repeated 
with the set reversed. From these the core loss of the set may 
be calculated. 

SPECIAL TESTS consist of saturation, core loss, input-output, 
commutation and field balancing tests. 

INPUT-OUTPUT TEST consists of taking careful measurement 
of the input and output of the set when connected .as during the 
heat runs. 

COMPLETE TEST consists of field balance and adjustment, 
normal and overload heat runs, core loss or input-output, and 
commutation tests. 

156 



CHAPTER 8 

DIRECT CURRENT MOTORS 

The tests on direct current motors may be divided in the 
same manner as for generators. 

Preliminary Tests are practically the same as those taken 
on d-c. generators and the instructions included in Chapter 7 
should be carefully followed. 

When the machine has been wired according to the correct 
print, the wiring should be checked by the Head of Section, or his 
assistant, and it is absolutely necessary that the machine should 
operate in the proper direction of rotation when so connected. 
Make provision for reading volts and amperes line, volts and 
amperes field and speed. Direct current motors may be loaded 
by the methods given in Chapter 7 or by belting to generators. 

Starting 

After setting the brushes on the mechanical neutral and 
observing instructions contained in Chapter 4, page 98, the 
machine may be started. You must be absolutely certain that 
there is a full field on any motor before attempting to start it. On 
starting, the speed of the machine must be carefully followed 
with a tachometer and the circuit breaker must immediately 
be opened if the speed rises above the prescribed limits. 

With the starting rheostat, or water box in the "off" posi- 
tion the terminals of the rheostat or box must be attached across 
the open main switch AFTER the circuit breaker has been 
closed. The lower terminal should be attached first. The 
resistance across the main switch may then gradually be cut 
out, and if the speed of the motor is all right, should be entirely 
cut out and the main switch closed. If the motor tends to run 
above normal speed, the circuit breaker must be opened and the 
motor shut down. The connections should be carefully checked 
to see that the field is wired properly. It may be that the field 
has been connected directly across the main switch. If such is 
the case the field current will fall rapidly as the starting resist- 
ance is cut out and the motor will speed up. To test for incorrect 
connections in the field, observe the volts field during starting. 
These will drop if the field is incorrectly connected. Trouble 
may also be experienced due to reversed polarity, etc., which 
may be traced out as noted under d-c. generators. 

MOTORS WITHOUT COMMUTATING POLES 
Adjustment for Speed and Commutation 

After the motor has been started it should be adjusted for 
commutation by shifting the brushes back of the mechanical 
neutral. This shift is necessary as the electrical neutral of a 
motor is shifted by the armature reaction in a direction opposite 
to the direction of rotation. When shifting brushes for com- 
mutation the speed of the motor must be carefully watched. 
With no-load normal voltage and full field a speed reading should 

157 



be taken, the brushes being shifted so that when full load is on, 
the speed is not less than 7 per cent below nor more than 3 per 
cent above normal rated speed. With the machine hot the 
speed must not vary more than 5 per cent either way from the 
normal rated speed, consequently the full load speed with the 
machine cold must be within the limits as given above. The 
same precautions regarding brush fit and the condition of the 
commutator should be used as for d-c. generators. 

All compound wound motors should be adjusted with full 
series field. If this cannot be done, the fact should be referred 
to the Head of Section. The speed must come within 4 per cent 
of the rated speed when the machine is hot. Differentially com- 
pound wound motors should be loaded with care since the series 
field may be strong enough to overcome the shunt field and cause 
the machine to speed up and run away. The no-load speed of 
accumulative compound wound motors should be carefully 
watched as it may be considerably higher than the rated speed. 
When the correct running position has been found it should be 
marked with a chisel and the number of bars shift from the 
neutral point recorded on the Testing Record. 

Speed Regulation 

Speed regulation may be defined as the ratio of the drop in 
speed from no load to full load divided by the full load speed. 
On a load run this regulation must not exceed 6 per cent. 

Heating Tests 

After the correct adjustment has been obtained the heating 
tests may be started. The general instructions in Chapters 4 
and 7 should be followed carefully. Motors may be loaded by 
belting to generators, feeding back, or by the circulating current 
methods described in Chapter 7. 

In using the method shown in Fig. 65, if the machines are 
motors, the same connections should be made and the machines 
thrown together. The voltage of the system must be held by 
the machine running as a generator. The only correct way of 
obtaining load is by changing the speed of the set, the brushes 
having previously been set in the running position. Usually 
the speed will have to be decreased and the difference between 
full load and no-load speed will be the normal drop in speed 
for the motors. Cases have occurred where the speed of the 
motor, due to armature reaction, increased during the load. 
In "feeding back," this fact is shown by the motor taking an 
overload at no-load speed in which case the speed of the loss 
supply must be increased. 

In using the method shown in Fig. 66, if two shunt motors are 
being tested, one machine should be run at normal voltage, 
current, speed and with full field; the other should be run as a 
generator with a little higher current and slightly stronger 
field than it would have under normal condition. The fields of 
the generator may have to be connected in multiple. The 
motor should be started first from the electrical loss supply 
circuit and its brushes shifted for commutation and speed. 

158 



After exciting the field of the generator and adjusting the voltage 
between the machines to zero the circuit may be closed. 
The machines should then be loaded by increasing the field cur- 
rent of the generator. The brushes must always be shifted 
carefully while the machines are under load, for a slight change 
in shift will at once change the load. During the heat run the 
speed will rise and the field current will fall. After the heat run 
has been finished and all motor readings taken, the wiring should 
be changed and the motor readings taken on the machine which 
ran as a generator. 

The circulating current method is used particularly in the 
testing of series or railway motors. In the latter case the 
machines are geared to the same shaft. 



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Fig. 74 
SPEED CURVES D-C. MOTORS 
Running Light 

Running light test should be taken on all motors at hot full 
load speed. The armature current required for running light 
must not be over 5 per cent of the full load current. 

SPECIAL TESTS consist of core loss, adjustment, commutation 
tests and speed curves. 

If special tests are required a hot speed curve should be 
included. From no load to full load, and including several 
intermediate points, the speed should be carefully read, the 

159 



voltage being held constant at all loads. A curve should then 
be plotted with speed as ordinates and amperes as abscissae. 
No load and full load points of a cold speed curve should also be 



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Fig. 75 
EFFICIENCY AND LOSSES ON A 70 H.P., 6 POLE, 850 R.P. 
500 VOLT D-C. MOTOR 



160 



taken. See Fig. 74. Some motors with a considerable armature 
reaction give a speed curve which rises as the load increases. 
All cases of rising speed curve must be referred to the Head of 
Section. 

COMPLETE TEST consists of normal and overload heat runs, 
saturation and core loss, speed curves and commutation tests. 

INPUT-OUTPUT TEST and OVER-SPEED TEST are taken in a 
similar manner as for generators. 

STANDARD EFFICIENCY TEST is made by the method of losses. 
Page 433 and Calculation Sheet 12 show the method used in 
calculating the efficiency of a d-c. motor. See Fig. 75. 

COMMUTATING POLE MOTORS 

Adjustment for Commutation 

The brushes of commutating pole motors should be placed 
on the mechanical neutral as explained under d-c. generators. 
The electrical neutral at no load should then be located by 
running the machine in both directions of rotation with the 
same field current, shifting the brushes, if necessary, until 
the speed comes the same in each direction. The machine should 
then be loaded with full commutating field and the commutation 
and speed carefully noted for each direction of rotation. If 
the commutating field is of the proper strength, commutation 
should be No. 1 (see Fig. 62). The full load speed of commutating 
pole motors when hot must be. within 5 per cent of the rated 
speed, and consequently the speed obtained on the above 
reading should not be less than 7 per cent below nor more than 
3 per cent above the rated speed, allowing for a 2 per cent rise 
in speed when the machine heats up. 

If the commutation is not satisfactory, or if the speed should 
increase from no load to full load, the commutating field should 
be shunted until black commutation and satisfactory speed is 
obtained. If with full commutating field the speed falls below 
the limit given above, the fact should be referred to the office, 
as no amount of shunting of the commutating field will bring 
the speed within the limit. With black commutation the motor 
should show a falling speed characteristic from no load to full 
load. If the speed rises more than one per cent within this range 
of load the fact should be referred to the Head of Section. 

If satisfactory adjustment cannot be obtained by shunting 
the commutating field, it may be that the field is too weak. In 
this case it should be separately excited with a current higher 
than that which would normally be obtained. If satisfactory 
adjustment is obtained under these conditions the fact should 
be referred to the Engineers to have changes made. 

After the correct adjustment has been obtained, the brush 
position should be chisel-marked and a cold speed curve taken. 
The speed and commutation in both directions of rotation up 
to the amount of overload specified in the testing instructions 
should be read and recorded. On DLC and RLC motors the 
brush-holder yoke should be securely doweled in position after 
tests are finished. 

161 



Some commutating pole motors show a tendency to "hunt" 
with full commutating field, but this can usually be eliminated 
by shunting the field. In all cases a notation should be made on 
the Testing Record regarding this point of stability. 

After the final adjustment, an ammeter should be wired in 
and the amount of current shunted recorded on the testing 
record. The machine may then be given the heat runs called 
for and after these have been taken and while the machine is hot, 
a hot speed curve should be taken using the same range of load 
as in the cold speed curve. 

Other tests are taken as previously described. Running 
light readings may be taken without disconnecting the series or 
commutating field, as the extra current required will be small. 

Motor and Generator Operation 

Quite frequently commutating pole machines are sent 
out as part of a motor-generator set, and required to operate 
as either a motor or generator. All such machines must have 
shunt adjustments made for both methods of operation while 
the machine is in test. Since the brushes are set on the no-load 
electrical neutral on almost all machines the same shift is 
proper for both motor and generator operation. The majority 
of machines, however, require a different adjustment of the 
commutating field shunt, for motor operation, to insure the 
proper speed characteristic. On the majority of commutating 
pole motors too strong a commutating field will cause the 
speed to increase as the load increases. This is never permissible. 
Current must be shunted from the commutating field till the 
speed at full load and overload is less than that at no-load, 
giving the motor speed a drooping characteristic. 

If a drooping characteristic and good commutation cannot 
be obtained with the same adjustment, notify the Head of 
Section at once, so that the proper steps may be taken to 
correct the trouble. Inductive shunts are used on both motors 
and generators, and the adjustment of the shunt is obtained 
in the same way in each case. In adjusting the commutating 
field shunt of a motor, however, the speed must be carefully 
noted, as well as the commutation after any change in the 
shunt is made. 

VARIABLE SPEED MOTORS 

The variations in speed of variable speed motors may be 
obtained by either armature or field control. 

Two methods of armature control may be used. The first 
consists in varying the resistance in the armature circuit and 
is used in work requiring no inherent regulation or constant 
load. The economy and inherent regulation by this method 
of control is poor. 

The second method of armature control consists in varying 
the voltage impressed on the motor armature only, the field 
remaining constant at its full value. The efficiency and regu- 
lation obtained by this method of control is good. 

162 



In the method of field control the brushes are set to give 
the best commutation at both speed limits. The variations 
in speed are then obtained by varying the field. 

Commutating pole variable speed motors must have the 
shunt in the commutating pole field adjusted for the highest 
rated speed. Speed curves and running light tests should be 
made at both speed limits. 

Shunt wound variable speed motors should have the brushes 
set for commutation at the speed limits. Speed curves and 
running light tests should be made at both these speeds. 

Some compound wound variable speed motors are not 
designed to run light, consequently before starting, the smallest 
load the motor is designed to carry should be ascertained. The 
Engineering Notice usually specifies the load at which the 
motor should start. Commutation should be adjusted at the 
speed limits and the speed carefully recorded. Speed curves 
should be taken at the speed limits. Running light should be 
taken at the various speeds. 

DIRECT CURRENT SERIES AND RAILWAY MOTORS 

The principal type of series motor is the railway motor. 
Other types, however, are built for use with hoists, air com- 
pressors, pumps, etc. As all these motors are designed for 
intermittent service, the test, unless otherwise specified in the 
Engineering Notice, is of one hour's duration at full load, 
the brushes being on the neutral point. The load must never 
be taken off a series motor unless the armature circuit is first 
opened, otherwise the motor will run away. For the same 
reason a series motor should always be started under load. 
All running light tests must, therefore, be made with the field 
separately excited. 

The speed of railway motors and other series motors when 
hot should never vary more than 3 per cent from the normal 
rating. 

As the tests on railway motors are very complete and their 
general method applies to any series motor, the tests on rail- 
way motors will be discussed more or less in detail. Hot and 
cold resistances must be taken on all railway motors. The 
cold resistances, when corrected to 25 deg. cent., must not vary 
more than 5 per cent from the standard resistance. 

High potential must always be applied while the motor 
is cold and hot. There are Standing Instructions specifying 
the degree of high potential to be applied to all parts of the 
different types of motors. 

GENERAL TESTS consist of sufficient preliminary tests to war- 
rant Engineering approval for production. It is impossible to 
define, definitely, the heading, since the tests may include only a 
few minor tests, or they may include Complete and Special Tests. 
For instance, it may be necessary to make slight changes, 
either in the construction or design of a standard motor in 
order that it may meet special requirements due to peculiar 
operating conditions, etc. After these changes have been made, 

163 



tests are conducted to insure the motor meeting such condi- 
tions satisfactorily. These tests are included under the general 
tests. If, after completion, they are found to be satisfactory, 
Engineering approval is given for the production of the machine 
in question. 

COMPLETE TESTS consist of special tests, thermal character- 
istics, commutation and input-output. With the exception of 
commutation, the other tests under this heading will be con- 
sidered separately. 



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CORE LOSS AND SPEED CURVE OF A 50 H.P., 500 VOLT 

RAILWAY MOTOR 



200 240 



Commutating tests on series railway motors should be 
made by holding normal voltage and operating the machine 
at loads varying from 33 ^ per cent to 200 per cent normal 
load. 

On series commutating pole motors, Interruption Tests 
are taken. These consist in opening and closing the motor 
circuit, while the machine is running at various loads and speeds. 
The machine should stand such tests without arcing over at a 

164 



line voltage as high as 125 per cent normal. The loads are 
varied from 33 }/& per cent to 200 per cent normal. Mill motors 
are tested for commutation by suddenly reversing the direction 
of rotation under various loads. 

DEVELOPMENT TESTS consist of General Tests and Special 
Tests, and are made when an entirely new type of machine is 
being developed. 

SPECIAL TESTS consist of speed curves, core loss, and satura- 
tion tests. 

In taking a speed curve two similar motors are mounted on 
a testing stand, the pinion of each meshing in the same gear 
on a shaft. One motor drives the other as a separately excited 
generator and is run loaded until the motor is heated to about 
50 deg. cent. rise. The speed curve is then taken on the motor 
rotating in both directions, the voltage being held constant. The 
resistance of both armature and field should be measured both 
before and after taking the curve. 

Core loss should be taken as on any other machine by the 
belted method, except that the test should be made at about 
five speeds. Fig. 76. The lowest speed should correspond 
to about 175 per cent full load amperes (taken from speed 
curves) and the highest at about 200 per cent full load speed. 
During this test the machine is separately excited. 

A saturation curve may be taken as on any other machine 
by separately exciting the field. Saturation curves at different 
speeds mav be obtained from data taken during the core loss 
test. 

The speed curves, core losses and saturation are calculated 
as previously explained. The speed curves and core losses 
should be plotted on the same sheet against amperes line as 
abscissae and rev. per min. and watts as ordinates. From these 
two sets of curves another can be developed, which will give the 
core loss of the motor at any speed or current. 

The Thermal Characteristic should be obtained by making 
a series of heat runs at varying amperes, allowing sufficient time 
to get a temperature rise of 75 deg. cent, on any part except the 
commutator. Each run should be made at the same constant 
voltage, the current value for each run varying from 50 to 150 
per cent normal. If a sufficient number of heat runs be taken 
on a sufficient number of motors of the same class, type and 
form, the horse-power rating for 75 deg. cent, rise may be 
obtained for any length of run from one-half hour to continuous 
running. Before starting a heat run, cold resistances and tem- 
peratures should be taken. After the motor has run continuously 
for the allotted time, amperes and volts having been held 
constant with all covers off, and all openings unrestricted, it is 
shut down, hot resistances measured, and all temperatures 
taken. The results of the thermal heat run should be plotted, 
one curve for armature and one for field, against time in hours 
as abscissas and degrees cent, rise as ordinates. Through zero 
and the plotted points corresponding to the different loads, lines 
should be drawn. The intersections of these lines with the line 

165 



of 75 deg. cent rise gives the time the motor takes to attain 75 
degrees rise with the load corresponding to the plotted point 
through which the line was drawn. From these curves another 
curve should be plotted with time as abscissa? and amperes load 
as ordinates. This is an ampere time curve for 75 deg. cent. rise. 



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THERMAL CHARACTERISTICS OF A 100 H.P., 600/1200 VOLT 

RAILWAY MOTOR 



On the same sheet as the ampere time curve is plotted, a curve 
should be drawn with time as abscissae and horse power as 
ordinates, the horse power being calculated from the standard 
75 deg. cent, characteristics. See Fig. 77. 

166 



In loading railway motors, as in the Speed Curve, two 
motors are geared together on the same shaft (see Fig. 78), 
one running as a motor at the rated voltage and full load current 
and driving the other as a separately excited generator. The 
separately excited field of the generator is in series with the 
motor field, thus giving a normal full load excitation. The 
armature of the generator is connected to a water box, the 
resistance of which is varied until full load on the motor is 
obtained. The run is made for one hour, after which temper- 
atures are taken. 



Motor 



[=|)j^a^j: JT==rt =#=) 



Generator 



"&O-0OOOO0O" 



fte/a 1 




Fig. 78 
CONNECTIONS FOR LOADING TWO RAILWAY MOTORS 



Resistances are measured and high potential applied both 
before and after the test, and, before starting, the speed should 
be checked in both directions of rotation. 

The circulating current method is often used in making this 
test. 

One out of every fifty of all types of motors should receive 
the one hour load run. All 600 volt commutating pole motors, 
excepting those receiving the one hour load run, should be run 
under load for ten minutes in each direction of rotation. Other 
motors having their characteristics well established should 
receive commercial tests. 

COMMERCIAL TESTS consist in running a motor light for a 
short period. It is the practice to run four motors in parallel, 
the fields being connected in series and separately excited by 

167 



a current equal to full load current of the motor. (See Sketch 
of Connections in Fig. 79.) 

With normal voltage held constant across the armatures, the 
motors are run light for five minutes in each direction of rotation, 
readings of speed, armature and field current being recorded. 

With rated voltage across the motors, the fields should be 
weakened until about twice normal speed is attained. Under 
these conditions the machine should be run in each direction 
for five minutes, the same readings as above being recorded. 

Resistance measurements cold only are taken. High poten- 
tial tests must be made after this run. 



Booster 




<& 



F/W/ F/e/SJ FMJZ Fi6>M4\ 



Fig. 79 
CONNECTIONS FOR RUNNING LIGHT ON RAILWAY MOTORS 



Care must be taken that the resistance at 25 degrees cent, 
and speed come within the prescribed limits already mentioned. 

STANDARD EFFICIENCY TESTS on all series motors with the 
exception of railway motors are made by the method of losses and 
the calculation is identical with that of any other motor. In 
this case, of course, the amperes armature equals amperes line. 
See page 433. 

In making an INPUT-OUTPUT TEST the motors are geared 
and connected as for the Load Heat Run and are usually run 
under full load for one hour up to ordinary working temperatures 
and to get the bearings in good running condition. Before 
the load is put on, a careful measurement of the armature and 
field resistances of the motor, and of the armature of the gener- 

168 



ator is taken by the drop in potential method. Three differen 
measurements of each should be made with as many different 
values of current, which should be near the normal load current. 
Holding constant normal voltage, 12 or 15 different loads 
ranging from as low as possible to 150 per cent load should 
be put on, the direction of rotation being such that the motor 
tends to lift from its bearings. Readings at each load should 
be taken of the amperes, volts armature and speed of the motor 
and amperes and volts armature of the generator. The direction 
of rotation should then be changed and several check points 
taken in speed and amperes, after which the machine should 
be shut down and hot resistance measurements made. 

/300 \ 
/200 .Vi 
J/OO ^ 

/ooo /oo 

900 30 
800 30 
7O0 70 



600 60 















































































































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/20 



Fig. 80 
INPUT-OUTPUT CURVES ON A 100 H.P., 600 VOLT, RAILWAY MOTOR 



Tractive effort 



The Calculation Sheet 8 and Fig. 80 show the method 

of working and plotting the data obtained from the input-output 

test. Unless otherwise specified the tractive effort and miles 

per hour are calculated for 33 in. wheels. The formulas used 

are: 

,,.. , R. p. m. X diameter of wheels in inches X-n- 

Miles per hour = — ■= : ,^„^ 

Gear ratio X 1056 

Amps. X volts X efficiency X 252 

Miles per hour X 500 

The gear ratio is that between the gear and pinion. 

From these characteristics new ones should be plotted, 
as shown in Fig. 81, the PR being corrected for 75 deg. cent, rise, 
and the gear loss assumed as 5 per cent at full load. If the gear 
loss from test has to be changed at full load, it should be changed 
in the same ratio throughout the curve. (See Calculation 
Sheet 9.) 

COOLING OFF TESTS are made by running the motor under 
full load, with covers off, for one hour, shutting down and reading 
temperatures as the machine cools down. For the first hour 

169 



after the machine is shut down, the following temperatures 
are read every fifteen minutes: the armature, commutator, 
field, frame, air in the motor, and room temperatures. After 
the first hour temperatures should be taken every half hour 
until the temperature of the hottest point is not more than 25 
degrees cent, above the surrounding atmosphere. 

The results of the cooling off test should be plotted to time as 
abscissas and degrees centigrade rise as ordinates. The curves for 
armature, field, commutator, frame and air in the motor, should 
all be plotted on one curve sheet. 











' uu ""rag 1) L, %c?/? 






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Amperes 



200 



260 



Fig. 81 

SPEED, TRACTIVE EFFORT, EFFICIENCY ON A 100 H.P., 600 VOLT 

RAILWAY MOTOR 



DYNAMOTORS 

Dynamotors are used to supply current at one-half the line 
voltage of a system and consist of an armature having two 
distinct windings and commutators rotating inside a common 
magnetic circuit, having a shunt winding and also a series 
winding so connected that it is active only during the period 
of starting. The tests ordinarily taken consist of dynamic 
balance of the armature in a special frame, a one hour heat run 
at rated output and running light readings with normal con- 
nections (but with the ground connection removed) and also 
at reduced voltage with the series field only. After these tests 
are finished the dynamotor should be thrown directly on the line 
and starting characteristics and commutation noted. 

Core loss when called for, should be taken by the method of 
motor core loss. Calculation Sheet 27 shows results of a motor 
core loss on this type of machine. 

170 



Input-output efficiency is calculated from the readings taken 
with the machine connected as for a heat run. Calculation Sheet 
26 shows results of such test. 

VENTILATION TESTS 

Ventilation tests are sometimes taken on Railway Motors. 
The double pitot tube method is ordinarily used and the velocity 
and quantity of air delivered calculated using the weight of the 
standard air. In this cas e 

V=401oV h 3 at the center of the pipe. 

Q =3654^4 V I13 using the average velocity as given 
in Chapter 16, page 313. 



17 



CHAPTER 9 

ALTERNATING CURRENT GENERATORS 

The tests on Alternating Current Generators may be divided 
as follows: Preliminary tests, commercial tests, heating tests, 
special tests, input-output tests, over-speed test, wave form, 
location of keyway, voltage regulation and static tests. 

Preliminary Tests consist of drop on spools, resistance 
measurement, air gap and fitting of collector brushes. The pre- 
cautions specified in Chapter 4 should be carefully followed. 

COMMERCIAL TESTS consist of excitation and other readings 
at no load necessary to demonstrate that the machine is a dupli- 
cate of the same type already shipped and that it is free from 
manufacturing defects. 

After the machine has been started a saturation curve should 
be taken as described in Chapter 6, page 120, the curve being 
taken up to full excitation voltage on the field. Care should be 
used to see that the voltages in the various phases are balanced. 

Synchronous impedance may then be taken. The object 
of this test is to determine the field current necessary to produce 
a given armature current when the machine is running short- 
circuited. Since the regulation of the machine is calculated from 
the impedance and saturation curves, care should be taken that 
consistent results are obtained. 

The armature . should first be short-circuited; then with 
the machine running at normal speed and a weak field current, 
the current in each phase should be read. The field current 
should be increased gradually until 150 per cent normal arma- 
ture current is reached, readings being taken simultaneously 
of amperes armature and field and volts field. Care should be 
taken not to overheat the windings. 

Although the speed in this test should be held normal a 

small variation therefrom will not affect the curve, because 

e.m.f. -E 

in the formula, current = = '— A = / „ ^ ^et the term R 2 

Impedance VR 2 +L 2 W 2 

is small compared with L 2 W 2 , and as E and W vary propor- 
tionally to the speed, the current remains practically constant. 
In the calculation of synchronous impedance all readings 
should be corrected for the constants of instruments and ratios 
used and a curve plotted on the same sheet as the saturation 
curve, amperes or ampere turns field being plotted as abscissae 
and amperes armature as ordinates. See Calculating Sheet 
7 and Fig. 82. 

Phase rotation should be taken after these tests are finished 
by using a "Phase Rotation Indicator" described in Chapter 2, 
page 25. See Fig. 12. The terminals of the machine under test 
whether three-phase or quarter-phase should be connected 
to the corresponding terminals of the indicator. The indicator 
should operate on the residual voltage of the alternator but if it 
will not, a small field current should be applied to the machine 

172 



under test and the voltage should gradually be brought up to a 
small amount and the magnet of the meter should revolve in the 
same direction as the rotor of the machine under test when 
facing the head end. Be careful not to burn out the indicator. 
If it rotates in the opposite direction (a) for a quarter-phase 
machine, a phase is reversed; (b) for a three-phase machine, either 
a phase is reversed or the wrong leads have been brought out. 
The head end of a machine is the end at which the coil to coil 



/OOO 




















S 


900 




















_ f 




















/ 


BOO 




















./ 




















r 


l**> 


















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*m 
















/ 




















r 

/ 




















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y 


' 


















/ 


















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\300 
§200 










/ 


















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/ 
















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/ 


















/ 


















°t 


/ 




















1 




A 





2 

s4/n 



'pert 


s / 


JO 
%vfc 


f 


<U) so 



Fig. 82 

SYNCHRONOUS IMPEDANCE CURVE ON A 500 KW., 600 VOLT 

360 R.P.M., 3-PHASE, 60 CYCLE, A-C. GENERATOR 



armature connections are made. Figs. 83 and 84 cover every 
type of standard connection block, and will assist in numbering 
the machine terminals for the phase rotation indicator. If the 
block is on the side of the machine facing the bearing, or on the 
outside of the frame proper and at right angles to the shaft, the 
numbers should read 1-2-3 in a clockwise direction. If the block 
is in any other position, as on the side facing the bearing with 
the numbers running radially, or on the frame proper with the 
numbering parallel to the shaft, the same sequence of numbers 
should exist, but the block has been given a quarter turn in a 
clockwise direction. In the case of revolving armatures the 
numbering is always from the inside ring toward the outer. 

Magnetic leakage sometimes causes a small e.m.f. to be 
generated which causes an alternating current to flow through 

173 



the frame of the machine to the shaft, resulting in the pitting 
and marring of the latter inside the bearing. A reading should 
be taken on all alternators of 200 kv-a. and above to ascertain 




\ Load End 



( 




\ 


i 


m 


)N 




"tT 


w/ 



Load End 



1 2 J 
O O O 






/ 2 
» o . o 
3 a. 
o o 




Clockwise 






1 2 
o o 

3 d 

o o 





13 
I • 

3 . 

4 4 




Commutator Collector 
For A 3 or A Moch/r>QS wrth' 
Revolving Shunt 



Connect -Studs land 3 to the some Phase on I Q and QB 
Connect Stud 3 to beginning of Phase / 
Connect Stud 4 to beginning op Phase 2 

Fig. 83 
CONNECTION BLOCKS 



whether there is any appreciable current flow from this source. 
A high reading a-c. ammeter should be connected to low resist- 
ance leads, one of which is in contact with the revolving shaft, 
and the other securely fastened to the frame of the machine.. 

174 



If an appreciable reading is obtained on the instrument, the fact 
should be reported as a defect to be remedied by insulating 
the bearing-standard from the base. 




V 



d Lead End 



J 



i 



^ 



uuu 
Lead £nd 



} 



I 3 5 7 

?z:zz--s 




A O Machines 
With Revolving Shunt 



5 ■ -^H 

s - 




Commutator Col lee tor for 
A T Machines Col lector Studs 
hove odd numbers, Commutator 
Studs have ever, numbers 



Fig. 84 
CONNECTION BLOCKS 



All machines rated 1000 kv-a. and above must be furnished 
with insulation under the bearing pedestal. 

HEATING TESTS 

Before starting these tests instructions in Chapter 4 regarding 
thermometers, etc., should be carefully followed. The heating 

175 



tests on a-c. generators may be divided into two parts; 
load tests and equivalent load tests. 



actual 



ACTUAL LOAD TESTS 



Actual load tests may be taken by the water box method or 
feeding-back method. 

The water box method is similar to that described for d-c. 
generators. Boxes must be used in each phase and care must 
be taken to keep the currents in the various phases balanced. 
The boxes in the different phases of a three-phase machine 
should be connected in "Y", and the leads from the generator 
under test should be run to the blades. Not more than 2300 
volts should be applied to the standard water box. Machines 
requiring a higher voltage than this should have transformers 
placed in the line. In the various sections there are several 
water boxes good for more than 2300 volts and these should 
be used whenever possible, rather than transformers. 




Fig. 85 

GRAPHICAL DETERMINATION OF CURRENTS 

FOR A POWER-FACTOR HEAT RUN 



Very often it is required to load an a-c. generator at a 
specified power-factor. In such case a synchronous motor should 
be connected across the terminals of the generator under test 
in multiple with the water boxes and should ordinarily be run 
light, having its field excited to give the required leading or 
lagging current in the armature circuit of the generator under 
test. If the latter machine is to be run at leading power-factor 
the field of the synchronous motor must be excited with a 
current above its normal excitation for unity power-factor. 
The machine under test is accordingly run below normal excita- 
tion. If a lagging power-factor is specified the conditions are 
reversed. Wattmeters must be used to determine the power- 
factor of the circuit. The amount of current to be held in the 
armature circuit of the synchronous motor floating on the line 
may be determined graphically as follows. Referring to Fig. 85: 

Let AB = full load current of the generator under test (for 
a normal load heat run.) 

176 



Draw angle BAC=the angle whose cosine is the power- 
factor to be held. 

Draw BC perpendicular to AC. 

Lay off CD = minimum input current for the synchronous 
motor running light. 

Then BD is the current to be held in the armature circuit 
of the synchronous motor and AD is the amount of current to 
be carried by the water boxes. Thus, by holding the synchro- 
nous motor current at BD (varying the field if necessary) and 
loading the generator under test on the water boxes until AD 
amperes are obtained the load of the specified power-factor is 
obtained and the heat run may be taken. 



OV 




Fig. 86 
SHIFTING OF PHASES SHOWN DIAGRAMMATICALLY 



"Feeding Back" Method 

Two similar alternators may be tested under actual load 
by direct connecting their shafts and supplying the losses 
mechanically. It is, however, necessary to shift the stators 
with respect to each other so that the machines will remain 
continually out of phase with each other. The vector difference 
of the voltages thus generated by the two machines will cause 
a current to flow which may be varied by changing the relative 
positions of the stators. For example, consider a three-phase 
machine the phases of which are shown diagrammatically in 
Fig. 86. The machines should be run at normal speed, with the 
fields separately excited to a value corresponding to the load 
at which it is desired to make the test. The value of this excita- 
tion should be calculated from the saturation and synchronous 

177 



impedance curves. With points a and a r connected together 
the voltage across b and b' should be read, the circuit closed 
and the value of the current flowing observed. Knowing the 
voltage between phases a-b, a'-b', and between b and b', the 
angle of phase displacement may be readily obtained. Should 
the armature current be considerably greater or less than that 
desired a further trial will be necessary. 

The current value will vary nearly as the angle of dis- 
placement so that an approximate value of the angle desired 
can be found from the value of current and angle previously 
ascertained. When the value of this angle has been ascertained, 
the phase displacement should be changed, so as to obtain it 
as closely as possible. With the machines still connected together 
as they were originally, the angle of phase displacement pre- 
viously found will be increased 120 electrical degrees by con- 
necting a' and b. If a' and c are connected, a still further 
displacement of 120 degrees is obtained. If with any of these 
connections, the field of one machine be reversed, a still further 
displacement of 180 degrees is made. With the connection which 
gives the nearest value of armature current to that required, 
a further adjustment may be made by shimming the stator of 
either or both machines up on one side and taking shims out on 
the other side. The circuits should then be closed and the heat 
run made for the specified time. Even with the angles of phase 
displacement possible with -the various combinations of con- 
nections and field reversals it may not be practicable to get the 
desired armature current. In this case, unbolt the coupling 
and shift the rotor of one machine around one or more 
bolt holes. The "cut and try" operation should then be 
repeated. 

Although thus "cut and try" method is not the best one to 
use it gives very satisfactory results, especially where it is 
necessary to make an actual full load test. 

Two frequency changer sets consisting of a-c. generators 
and synchronous motors may also be given an actual load run 
by shifting the phases of the generators or motors with respect 
to each other. The losses in the sets should be supplied electri- 
cally from the synchronous motor end. The stators of the gener- 
ators or motors are usually held in cradles, so that they may 
be rotated to run in phase with other machines, consequently 
it is necessary only to turn the frames in their cradles to obtain 
the proper shift. Each different load of course requires a 
definite relative position of the two stators. The fields should 
be excited with the field currents necessary for the test as found 
from the saturation and synchronous impedance curves. One 
set will operate direct and the other inverted. 

If a run is required at a specified power-factor the generator 
of the set operating inverted should have its field excited at such 
a value that the specified power-factor is obtained on the gener- 
ator of the set operating normally. Wattmeters should be 
used to determine the power-factor. 

178 



EQUIVALENT LOAD TESTS 

Equivalent Load Tests may be subdivided into "Open 
Circuit Heat Run," "Short Circuit Heat Run," "Open Delta 
Heat Run" and "Zero Power-Factor Heat Run." 

The Open-Circuit Heat Run as its name implies consists in 
running the generator at no load and with a field current which 
gives a predetermined percentage over normal voltage. The 
run should be continued until the temperatures are constant 
and the machine then shut down and the final temperatures 
recorded. The resistance of the field should be measured care- 
fully both before and after the run. Volts armature and speed 
should be held constant and readings taken of volts and amperes 
field. 

The Short-Circuit Heat Run consists of running the machine 
until temperatures are constant with its armature terminals 
short-circuited through an ammeter and with sufficient excitation 
in the field to obtain a given percentage over normal current in 
the armature. Amperes armature and speed should be held 
constant and readings taken of amperes and volts field. Final 
temperatures should be recorded and the resistance of the 
armature both before and after the run carefully measured. 

The Open Delta Heat Run is sometimes made on large three- 
phase alternators. The phases of the machine should be 
connected in delta, one side of which is left open. The 
machine should be run up to speed, the field excited and 
the voltage across the opening in the delta measured with a 
potential transformer and voltmeter. This voltage should be 
approximately zero. The armature should then be wired to a 
source of direct current sufficient to supply the amount necessary. 
One side of the open delta should be grounded to protect the 
armature of the direct current machine from static strain. 
The other armature terminals should be carefully insulated. 
Due to harmonics which may exist in the legs of the delta, an 
alternating cross-current may flow in the winding. This should 
be measured by an a-c. ammeter and current transformer (if 
necessary) inserted in the armature circuit. The amount of 
circulating direct current necessary is then found as follows: 

Let / = normal rated current of machine under test. 
V = normal rated voltage of machine under test. 

^ T rated kv-a. 

then / = ;= 

V3 V 
Let I\ = amount of cross current found with field excited as 
specified above. 

h= amount of direct current required. 
Then P = Ii>+I 2 * 
I 2 2 =P-Ii 2 
When this value has been determined the voltage of the machine 
supplying the circulating direct current should be increased 
until the desired current is obtained. The field of the alternator 
under test should then be excited to the value necessary to give 
normal no-load voltage, and the run continued until tempera- 

179 



tures are constant. Careful record should be made of volts 
armature, volts and amperes field, direct- and alternating- 
current amperes armature, and speed. 



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Fig. 87 

EFFICIENCY AND LOSSES ON A 5000 KW., 11,000 VOLT, 257 R.P.M. 

60 CYCLE, 3-PHASE A-C. GENERATOR 

The Zero Power-Factor Run is another excellent method of 
making an equivalent load run and is often used where two 
machines of approximately the same rating are available. The 

180 



generator under test is run as a synchronous motor with its 
field excited to give full load current. The field is usually over- 
excited, but there may be cases when under-excitation is specified 
or a test may be called for in which the field will be intermittently 
over- and under-excited. Readings should be recorded of amperes 
armature, volts armature, amperes and volts field and speed, 
and the run continued until all temperatures are constant. 
Final temperatures should then be taken and the resistances 
of both field and armature carefully measured. 

SPECIAL TESTS consist of saturation, synchronous impedance, 
open- and short-circuit core loss and wave form. On turbine 
driven generators air readings will be taken to determine the 
pressure and amount of air circulating in the various parts of the 
machine. 

INPUT-OUTPUT TEST, OVER-SPEED TEST and WAVE FORM 
have been described in Chapter 6. 

COMPLETE TEST consists of special tests and heating tests. 

STANDARD EFFICIENCY TEST is made by the method of losses. 
Page 437 and Calculation Sheet 14 and Fig. 87 show the method 
of calculating and plotting results. 

LOCATION OF KEYWAY 

It is often required that two machines whose revolving parts 
are on the same shaft, or are to be direct connected shall operate 
in series or multiple. In such case the generated voltages must 
be in phase with each other, and in order to make sure of this 
fact the key-ways of the machines must be definitely located 
with respect to each other. This is done by connecting the 
fields of the two machines in series and exciting them from the 
same source of power. The revolving parts are then adjusted 
and the keyways so located, that upon suddenly opening the 
field switch, no "kick" is obtained upon a voltmeter connected 
across any particular phase of either machine. This position 
can best be determined in the following way: Set the rotating 
part of the first machine with respect to the stationary part so 
that no "kick" is obtained on a voltmeter across any one phase 
when the field circuit is suddenly opened. Then set the other 
machine so that zero "kick" is obtained on that phase which is 
to be connected to the phase of the first machine on which zero 
"kick" was obtained. A definite marking should be made upon 
the machines so that the shop may cut the key-ways in such 
position that the relative position of the rotors will always 
remain the same. 

VOLTAGE REGULATION 

A test of the voltage regulation of alternating current gener- 
ators is sometimes made, but more frequently is calculated from 
the saturation and synchronous impedance curves. In actually 
determining the regulation, the machine is subjected to normal 
load with normal voltage held on the armature. With the field 
excitation held constant, the load is suddenly thrown off and the 
armature voltage observed. The difference between this 
voltage and normal voltage divided by the normal voltage is 

181 



the per cent voltage regulation. Very often, especially on large 
machines, it is found impossible to run the machine at actual 
load on account of limited facilities. In such cases it becomes 
necessary to calculate the voltage regulation from the saturation 
and synchronous impedance test. This is done as follows: 
Let V = normal line voltage. 

/ = normal line amperes 

R =hot resistance between lines. 

r . ^ , , . rated kv-a. 
I for three-phase machines = 7^ 

Vs v 

T , , , . rated kv-a. 

I for two-phase machines = -r-== 

2V 

= voltage drop in armature for three-phase 

machines. 

v = IR = voltage drop in armature for two-phase 
machines. 

Let ai = amperes field on saturation curve corresponding 
to(F+»). 

a 2 = amperes field on synchronous impedance curve 
corresponding to J. 

The amperes field required to produce n ormal ra ted voltage 
with full load on the generator will be a s = var+^2 2 . 

Let Fi=the voltage on the saturation curve corresponding 

to a 3 . 

Vi — V 
Then per cent regulation = — ^ — 

If it is desired to calculate the regulation of the machine at a 

power-factor less than unity then I becomes- — ? — - — 

per cent power-factor 

and as becomes Vai 2 +a 2 2 — 2a x a 2 sin where = the angle whose 
cosine is the power-factor. 

STATIC TESTS 

Some perfectly standard a-c. generators are given what is 
known as "Static Test." The resistance and polarity of the 
field spools are measured and the stationary armature is con- 
nected to an alternator of the correct frequency and the voltage 
necessary to overcome the impedance of the winding is measured 
at several different current values up to 200 per cent normal. 
Care should be taken not to overheat the windings. For this 
test the machine is not assembled in bearings, but the field 
is placed inside the armature and the air gap measured, after 
which, the field is removed and the impedance test taken. 

WAVE FORM 

Wave form is taken with the oscillograph and ordinarily at 
no load. The Engineers may, however, specify a full load test. 
In this case the machine is usually "dead-loaded" to eliminate 
the effect of the wave form of other machines. 

182 



CHAPTER 10 

SYNCHRONOUS MOTORS 

The tests on synchronous motors may be divided as follows: 
Preliminary Tests; Commercial Tests; Heating Tests; Special 
Tests; Input-Output; Over-Speed; Wave Form; and Torque Tests. 

Preliminary Tests consist of drop on spools, resistance 
measurement, air gap and fitting of collector brushes. The 
instructions in Chapter 4 should be carefully followed. 

When a machine is run as a synchronous motor extreme care 
should be used in starting it to see that the field circuit is open 
and that the voltmeter switch is not closed. The special switch 
designed for this case must always be used. The field of the 
synchronous motor acts as the secondary of a transformer, and 
the voltage induced across the rings at starting may be enough 
to cause serious injury As the machine comes to synchronism 
this induced voltage falls to zero and the field switch may then 
be closed. 

COMMERCIAL TESTS consist of excitation and other readings at 
no load necessary to demonstrate that the machine is a duplicate 
electrically of machines of the same type already shipped and 
that it is free from manufacturing defects. 

Synchronous motors are ordinarily run as a-c. generators 
when commercial tests are taken. 

HEATING TESTS 

Heating Tests on synchronous motors as on other machines 
consist of actual load tests and equivalent load tests. In 
making an actual load test the machine is usually excited with 
a current to give minimum input on the armature as found from 
the phase characteristic curves which are taken as follows: 

PHASE CHARACTERISTIC 

The machine must be operated from some a-c. source of 
correct frequency and at constant voltage. A reading of amperes 
input on all phases should be taken with zero field on the motor, 
where possible. Starting with a weak field and reading volts 
and amperes armature and volts and amperes field, the field 
should be increased by small steps until the point of minimum 
input armature current is found. Increasing the field current 
beyond this point increases the amperes armature. On a no-load 
phase characteristic curve, the watts input at the lowest point 
should check very closely with the sum of the core loss, friction 
and windage losses, since the power-factor is unity on synchro- 
nous motors at this point and the amperes field must equal that 
found for normal voltage on the saturation curve. These points 
must be checked with each other to see that they agree. With a 
weak field the current is lagging and with a strong field it is 
leading. In taking a no-load phase characteristic the current 
should rise to a value of at least 50 per cent of full load alter- 
nating current. 

A load phase characteristic should be taken in a similar 
manner to the no-load. The output is held constant and the 
amperes load recorded in addition to the readings noted above. 

183 



Care must be taken not to overheat the windings. It is 
impossible to obtain a zero field point during the full load 
characteristic, since the current would be so large as dangerously 
to heat the machine and the torque not sufficient to carry full 
load output. 



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PHASE CHARACTERISTIC CURVES ON A 187 KV-A., 2300 VOLT, 

720 R.P.M., 3-PHASE, 60 CYCLE, SYNCHRONOUS MOTOR 



All readings should be corrected for instruments and shunt 
ratios and a curve plotted between amperes field as abscissae 
and amperes armature as ordinates. See Calculating Sheet 10 
and Fig. 88. 

184 



ACTUAL LOAD TESTS 

The actual load test on a synchronous motor is usually made 
by belting or direct connecting the motor to a d-c. shop generator 
and exciting the field of the motor for minimum input as found 
above. 

In taking a power-factor heat run, the field of the synchronous 
motor should be over-excited to give the required power-factor 
unless otherwise specified. Wattmeters should be used to 
determine the power-factor. 

Synchronous motors which are parts of Frequency Changer 
sets may be given an actual load run as explained under a-c. 
generators. 

EQUIVALENT LOAD TESTS 

Synchronous motors are usually run as a-c. generators when 
being given equivalent load test. 

Sometimes a synchronous motor is given an equivalent load 
run by loading it on a d-c. generator and running at reduced 
voltage, having the load brought up to cause full load current 
to flow in the armature, and having the field held at the value 
which may be specified. 

SPECIAL TESTS 

On synchronous motors consist of starting test, saturation, no 
load and full load phase characteristics, synchronous impedance, 
core losses and wave form. 

Saturation, synchronous impedance, core losses and wave 
form are taken as for a-c. generators. 

Starting Tests 

Starting tests are taken as follows: If the motor is of a new 
type and rating, starting tests should be made both with and 
without a compensator. In all cases, however, the motor should 
first be tested without the compensator. 

The center line of one pole should be placed in line with the 
center line of the frame. At the head end of the motor a distance 
of 180 electrical degrees should be marked off in a clockwise 
direction from this line. The total length of the scale used should 
be %$ of the distance between the center lines of adjacent poles 
for three-phase machines, 3^ for two-phase machines and ^i for 
six-phase machines. The scales should be divided into five equal 
parts, each division line being numbered. On each one of these 
scale divisions the center line of the marked pole should be placed 
and the motor started. Thus five tests are made to insure that 
the motor will not stick in any position. See Fig. 89. 

With one pole moved to position No. 1 and the machine 
at rest, sufficient current should be sent through the armature 
to give a reasonable reading of amperes and volts on the various 
phases and induced volts on the field. The induced volts field 
should be read with a potential transformer and a-c. voltmeter. 
The readings with the machine at rest are taken to determine 
which phase gives the maximum readings of current and voltage 
so that the latter can be read at the moment of starting. 

185 



With the instrument switches adjusted to give the maximum 
reading, the armature current should be increased until the motor 
starts. Volts armature, amperes armature and induced volts 
field should be read simultaneously. The starting volts should 
now be held constant until the motor comes to synchronism, 
the time required to reach this point being recorded. The 
machine attains synchronism when the induced -volts on the 
field fall to zero. Then the machine should be shut down and 
the tests repeated from each of the other four positions. 

Enough time must be allowed between readings so as not to 
overheat the machine and the current must be left on only so 
long as is necessary to obtain a reading. 



"1*^ 



Pole, 




Fig. 89 

METHOD OF DIVIDING POLE ARC FOR STARTING TEST ON A 

3-PHASE MACHINE 



If a motor shows a tendency to remain at half speed the 
alternating voltage should be increased until the motor breaks 
from half speed and comes up to synchronism. The voltage 
required to break the motor from half speed should then be held 
and recorded until full speed is reached. 

All starting tests should be recorded on a special record sheet 
provided for the purpose and a sketch made showing the starting 
positions. If the motor sticks at half speed a record should be 
made of this fact. 

If the test is required with a compensator, the motor should 
be set with its field in the position where the highest starting 
current is taken and allowed to rest in that position for at least 
six hours until the oil is well pressed out of the bearings. This 
is done in order to obtain the worst starting conditions likely 
to occur in normal operation. Connections should then be made 
to the lowest tap of the compensator and with normal voltage 
held on the line, the starting switch of the compensator should 
be closed. If the motor fails to start, the voltage must at once 
be switched off and connections made with the next higher taps 
on the compensator and so on until the motor starts. Readings 

186 



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EFFICIENCY AND LOSSES ON A 1070 H.P., 13,200 VOLT, 500 R.P.M. 
25 CYCLE, 3-PHASE SYNCHRONOUS MOTOR 



should be taken at rest on each of the taps of the compensator 
in the starting position to determine the voltage ratio of the taps 
of the compensator. All these tests should be made with the 
field circuit of the motor open. During the test with the com- 
pensator, enough time should be taken between the trials to allow 
the compensator to cool, as it is designed for intermittent service 
onlv. See Calculation Sheet 24. 

INPUT- OUTPUT, OVER-SPEED and WAVE FORM have been 
described. 

187 



COMPLETE TEST consists of special tests together with normal 
and overload heat runs at unity power-factor. 

STANDARD EFFICIENCY TEST is made by the method of losses, 
page 439 and Calculation Sheet 15 and Fig. 90 show the method 
of calculating and plotting results. 

Impedance-Position Curves 

An impedance position curve is taken in the same manner 
as given for Induction Motors on page 215. A curve should be 
plotted using the average current per phase as ordinates and 
position number as abscissae. 

Torque Tests 

Torque tests may be divided into stationary torque and 
running torque tests. 

Stationary Torque tests are made in a similar manner to that 
given for Induction Motors on page 220, using a spring balance 
and lever. The rotor is blocked in the position which gives an 
average of the average current per phase as shown by the 
impedance-position curve, which should always be taken on a 
synchronous motor before stationary torque tests. Care must 
be used to allow sufficient time between readings and to take 
readings quickly enough so as not to overheat the windings. 

Running Torque is taken by running the motor with no field 
excitation and belted to a d-c. generator, the voltage and fre- 
quency of the motor being held constant. The voltage is usually 
held at one-half the rated voltage of the machine. The field 
on the belted generator should be held constant at such a value 
that approximately its normal voltage will be obtained with full 
speed on the synchronous motor. The brushes used for reading 
voltage on the d-c. machine should be insulated from the holders. 
Readings should be taken of volts armature (held constant), 
amperes armature, watts and speed of the motor under test; 
and volts and amperes armature, amperes field and speed of the 
d-c. generator. With no field on the d-c. generator the motor 
should be started and brought up to as near synchronous speed as 
it will come, and all readings then taken. Then with field on the 
d-c. generator but with no load, the test is repeated. The d-c. 
generator should then be lightly loaded and a new set of readings 
taken. These tests should be repeated with small increments 
in load to give about 5 per cent change in the final speed of the 
motor and should be continued until a reading is obtained with at 
least 200 per cent of the rated current of the motor. Watch 
the motor and do not let it become overheated. The tachom- 
eter should be checked at all speeds, and care should be taken 
to use the proper signs for the wattmeters'. After the above 
readings are completed the belt should be removed and running 
light readings obtained at all speeds used in taking the torque 
tests. The same field current should be held as in the original 
test. Curves may then be plotted with speed as abscissae and 
kw. output and torque as ordinates. 

188 



Calculation Sheet No. 23 shows the form used in calculating 
a running torque test, and Fig. 91 shows the method of plotting 
the curve. 



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Fig. 91 

RUNNING TORQUE CURVE ON A 75 KV-A., 2300 VOLT, 276 R.P.M. 

3-PHASE, 60 CYCLE, SYNCHRONOUS MOTOR 



189 



CHAPTER 11 

SYNCHRONOUS CONVERTERS 

Inasmuch as a synchronous converter is a combination of 
a direct current generator and a synchronous motor the tests 
taken are somewhat similar to those for the individual machines 
with certain modifications. 

Preliminary Tests consist of drop and polarity, cold resist- 
ance measure, air gap, checking of equalizer and collector 
ring taps, and other tests as specified in Chapters 4, 7 and 10. 

It is very important that any error in the winding or assembly 
of field coils be discovered at the time drop and polarity tests 
are taken, as most converters do not have their series fields con- 
nected in for test, and hence any reversed series field polarity 
would not otherwise be discovered before shipment. Reliance 
should not be placed on the compass, but the polarity of adjacent 
poles should be tested out with two iron bars. 

The machine should be examined to see that the bridges 
on the pole pieces do not project beyond the end of the pole 
face. The air gap measured between such projecting bridges 
and the armature is not the effective gap of the machine and 
any such projections should be reported as a defect if the gap is 
less than the normal gap. 

The cold resistance of the armature must be carefully 
measured between the different collector rings. On a three- 
phase armature, measure between rings 1-2, 1-3, 2-3; on a 
quarter-phase armature, between rings 1-3, 2-4; on a six-phase 
armature, between rings 1-4, 2-5, 3-6. The resistance of each 
circuit for any particular style armature should be the same. 
Ring No. 1 is always the one nearest the armature. 

The cold resistance of each field circuit should be measured 
and recorded. 

If necessary the commutator should be baked and trued 
as for a d-c. generator. 

The spacing of the equalizer and collector ring taps should 
be closely checked by counting the coils from each tap to the 
next. Occasionally a wrong connection is made, and if not 
corrected before the machine is run, one or more leads may be 
burned off and considerable damage done to the armature. 

Before any machine is started the wiring should be checked 
by the Head or Assistant Head of Section and the machine 
must operate correctly when connected according to the proper 
diagram of connections. 

Short Commercial Test 

Short Commercial Test consists in operating the machine at 
no load for certain definite tests to demonstrate that it is a 
duplicate electrically of machines of the same type already 
shipped, and that it is free from manufacturing defects. For 
this test the machine should be run for one hour as an inverted 
converter at 110 per cent normal volts across the rings. No- 

190 



load voltage ratio, balance across rings and running light readings 
from the d-c. end should be taken. Bearing temperatures should 
be read. 

Speed Limit and End Play Devices 

As soon as the machine is running properly the speed limit 
device should be adjusted to operate as described in Chapter 6. 

The end play should then be tried out to see that the field 
poles and armature are correctly aligned. The machine must 
be set level and the end play should be equal in both directions. 
The end plav device should then be adjusted as described in 
Chapter 6. 

Phase Rotation 

Phase rotation should then be taken to see that the collector 
rings are connected to the correct taps on the armature. This 
test is made by running the machine from the d-c. end and 
using the phase rotation indicator described in Chapter 2. 

Brush Setting 

Since very little armature reaction occurs in a converter the 
brushes should be set on the mechanical neutral. It may be 
found, however, that a slight shift from the neutral may give 
better commutation under load. 

Voltage Ratio 

The measurement of the ratio of the alternating to the direct 
voltage of a converter is one of the important tests and care 
should be used to obtain accurate results. The machine may 
be driven from either the a-c. or d-c. end, but a statement as to 
which method was used must be entered on the Testing Record. 
When running from the a-c. end, the field should be held at that 
value which gives unity power-factor as found from the phase 
characteristic. 

In order to check the accuracy of the instruments, two a-c. 
voltmeters, two potential transformers and two d-c. volt- 
meters should always be used. During the tests the direct 
voltage is held constant, and the alternating voltage read 
between rings 1-2 on three-phase, 1-3 on two-phase, and 1-4 
on six-phase machines. 

The ratio is taken at no load and full load and should be as 
follows when taken with the machine running from the a-c. end: 

No Load Full Load 
With direct current 
Single-phase 

Two-phase (measured on diam.) 
Three-phase 

Six-phase (measured on diam.) 
Six-phase (measured on adj. rings) 
Six-phase (measured on alternate rings) 

Converters with commutating poles may give values \]/2 
per cent greater than the above. 

191 



00 


100 


71.5 


73 


71.5 


73 


61 


62.5 


71.5 


73 


35.8 


36.5 


61 


62.5 



The amount of pole face arc will change the ratio. Any 
variation from these values greater than .2 per cent must be 
referred to the Head of Section, so that it may be investigated 
and brought to the attention of the Engineers. 

The standard shunt wound converter gives a very nearly 
constant ratio of alternating to direct volts at all loads, so any 
fluctuation in the a-c. supply affects directly the direct voltage 
delivered. Such machines are unsatisfactory when much varia- 
tion in load occurs. 

When it is required to vary the direct voltage on such stand- 
ard, machines, the applied alternating voltage must be changed. 
This may be done by using transformers with a dial switch, or by 
an induction regulator, or a synchronous a-c. booster. 

By adding a series field winding to the standard machine 
if it is required to operate with sudden changes of load, a practi- 
cally constant voltage can be obtained either by introducing 
reactance into the a-c. circuit, or by making use of the inductance 
inherent in its feeder circuit. This is possible since an alternating 
current passing over an inductive circuit will decrease the 
potential if lagging and increase it if leading. 

A converter running as a synchronous motor requires a 
certain field excitation to give the minimum input current to the 
armature. Varying the excitation either way changes the 
input current, so, by using sufficient reactance in the a-c. 
circuit from which the converter receives its power, the alter- 
nating voltage at the converter terminals may be increased or 
decreased by increasing or decreasing the exciting current. By 
adjusting the shunt excitation of the compound wound machine 
so it gives a no-load lagging current of about 25 per cent of full 
load current, and adjusting the series field to give a slightly 
leading current at full load, the impressed voltage at no load 
will be lowered and that of full load increased automatically. 
Hence with proper adjustment of the series field and sufficient 
reactance, the same direct voltage will be delivered at no load 
and full load. 

The ratio may be independently varied by making use of a 
split field-pole, as in "Split Pole Converters." 

HEATING TESTS 

The heating tests taken on converters usually consist of 
actual load test taken either by the "water box," "feeding 
back" or "circulating current" method. 

« 'Water Box" Method 

When loading a converter on a water box see that all cables 
from the transformers to dynamometer boards and to the 
a-c. rings of the machine are of the same length and capacity. 
All contacts must be cleaned and brightened before connection. 
Equal resistance will thus be obtained per phase and unbalancing 
in the a-c. circuits external to the armature prevented. In 
wiring the d-c. circuit the series field and its shunt are discon- 
nected. 

192 



In wiring converters, as with all other high current d-c. 
machines, both sides of the circuit should be laid close to one 
another. No iron, such as a bearing pedestal or a section of the 
frame, must lie within the loop of the circuit, since it will become 
magnetized and materially affect the operation of the machine 
and instruments. Always divide the shunt field into at least 
four sections, by a "break-up switch." This switch must 
always be open while starting from the a-c. end, since due to 
transformer action and relative number of turns of the field 
and armature, a high voltage is induced in the field at starting. 

Always wire the positive brush ring of the machine through 
a breaker to the blade of the water box, and the negative ring 
to the box of the water box. Connect enough boxes in multiple 
so that none will be overloaded. Make provisions for reading 
amperes and volts armature (a-c. side) ; amperes and volts 
armature, amperes and volts field (d-c. side) and the speed of 
the alternator. 

To start the machine close the a-c. line switches and the 
field switch of the driving alternator. Increase the excitation 
of the alternator, keeping close watch on the current in the a-c. 
lines. If this current reaches 150 per cent normal before the 
converter starts, check over the wiring and report to the Head of 
Section. If the machine starts rotating in the wrong direction, 
reverse two of the leads on the primary side of the transformers. 
After starting, as soon as the alternating current drops to the 
minimum value, showing the machine is in synchronism, and 
the alternating volts are normal, close the field ' ' break-up switch. ' ' 
If, after closing the shunt field switch, the brushes begin to spark, 
the residual magnetism left in the poles by the induced voltage 
at starting is of the wrong polarity. 

Two methods can be used to correct this. First, reverse 
the field with respect to the armature by flashing with the field 
reversing switch. Second, reverse the residual polarity by open- 
ing the alternator field switches. Then close this circuit and 
bring the converter back into synchronism, repeating this oper- 
ation if necessary until the field builds up in the right direction. 

Before proceeding further read the current in each phase to 
make sure there is no unbalancing. These currents should not 
vary more than one per cent from the average; any greater 
variation due to wiring must be remedied at once. 

After balance is obtained the no-load phase characteristic 
should be taken in a similar manner as for a synchronous motor, 
and holding the direct voltage constant. The machine may 
then be loaded and the full load phase characteristic similarly 
taken holding the direct voltage and current the same for each 
value of field current. (See Calculation Sheet 6.) At the point 
of minimum input the ratio of alternating to direct current 
should be as follows: 

Three-phase, alternating and direct current practically the 
same. 

Two-phase, alternating current equal to % the direct current. 
Six-phase, alternating current equal to Y2 the direct current. 

193 



These operations having been completed, the full load heat 
run may be started after the brushes have been set for the best 
commutation. On the load run hold full load d-c. amperes and 
direct volts constant, with minimum input field current. When 
holding minimum input by means of wattmeters make sure that 
they are connected to the proper rings, otherwise they may show 
unity power-factor when in reality the actual amount being held 
is about 60 per cent. The load should be kept on at least one 



£ty/?a/7?o/j7e£er£0asz/ 




tfeosterfo St/jOp/ySfo/fo/' I*/? losses 



Fig. 92 

CONNECTIONS FOR LOADING SYNCHRONOUS CONVERTERS 

WITHOUT THE USE OF A REGULATOR 

hour after all temperatures are constant, and at the end of the run 
temperatures must be taken on all parts of the machine, and the 
resistance measured on the armature (from the a-c. end) and 
on all field circuits. 

If an overload run is required an overload phase character- 
istic should be taken similarly to the full load. The direct volt- 
age should be held constant at the normal rating and the amperes 
output constant at the required overload value. The field 
excitation should be varied through as near the same range used 
on the full load as possible. The heat run should then be applied 
for the specified time and care should be taken that the time 
does not run over the limit. 

194 



With Boosters in the D-C. Side (Circulating Current Method) 

Fig." 92 shows the connections for two three-phase con- 
verters wired for a feed back heat run, without a potential 
regulator to control the load. The core losses and PR losses 
are supplied from the d-c. end. The diagram shows, also, 
the standard starting panel which should always be used when 
two converters are tested together. 

To start the machine, choosing No. 1 for instance, close the 
shunt field switch and switches K and K l which short-circuit the 
armatures of the loss supply. Note that the shunt fields are wired 
across the core loss supply, which is wired to busses B and C 
of the starting panel, and that the series fields are left open. 
Throw switch A to the left and slowly reduce the resistance of 
the water box till it is practically short-circuited, when switch 
5 may be closed. The blade of the water box should then be 
drawn out of the water and the switch A thrown to the right. 
Machine No. 2 is then started in a similar manner. 

The strength of the field of each machine is then decreased 
until they both run at normal speed. (See cautions on page 203 
regarding inverted converters.) Now connect a number of 
incandescent lamps in series, of which the rated voltage is 
equal to the sum of the machine voltage across rings aa', viz., 
across switches located on the dynamometer board. Two sets 
of lamps should be provided, one being connected across one 
of the switches while the other is used to step across each of the 
other switches in turn. Should one set show a rise and fall in 
voltage directly opposite to that of the other, the two phases are 
reversed, and must be corrected. When all phases show a 
simultaneous rise and fall, the machines may be phased together, 
bringing their speeds to the same value by changing the field on 
one of them. When the rise and fall of voltage shown by the 
lamps decreases to a period of 5 seconds or longer, close all the 
switches simultaneously, when the lamps are dark. 

Never close a single switch on the a-c. end as this would make 
a short-circuit on the armature. 

During the period of starting and phasing the machines 
together, the boosters should be short-circuited, with open 
fields. When the machines are synchronized the short-cir- 
cuits are removed. Apply a weak field on the booster and 
watch the line ammeter on No. 1. The reading of this ammeter 
should reverse from that given on motor load if No. 1 is taking 
load as a converter. By reversing the booster field either 
machine can be made to run as a converter. 

After balancing the current in each phase, the full load phase 
characteristic may be taken. The speed should be held constant 
by varying the field of the inverted converter, and the load held 
constant with the boosters while the shunt field of the converter 
is varied throughout its range and readings of current input 
carefully taken. Full load voltage ratio should then be taken 
after which the heat runs may be made. 

A line ammeter-shunt must be used in each side of the d-c. 
circuits. The currents flowing through them must have equal 

195 



values, otherwise one line has more resistance than the other, the 
unbalanced current returning through the a-c. ends - of the 
machines. The currents in these lines can be balanced by 
decreasing the resistance of copper to the low reading line. 
The direct currents should be balanced before attempting to 
balance those in the a-c. side. Two boosters for supplying the 
PR losses are necessary to eliminate unbalancing. 

In running this test there will be a slight difference in the 
direct voltages equal to the IR drop of the machines. The 
field of the inverted machine will be less than that required 
for minimum input. 



Inisertecf 
Converter- 



roTob/e 



ToTcrb/e 




7brab/e 
anc/Boxes. 



Fig. 93 

CONNECTIONS FOR FEEDING BACK SYNCHRONOUS CONVERTERS 

WITH REGULATOR 



This method of supplying the PR losses with boosters 
requires such large low voltage boosters that it is not often used 
except for small converters. 

With a Regulator in the A-C. Side (Feeding Back Method) 
Using D-C. Loss Supply 

A second method of testing converters for actual load 
heat runs, is to use a voltage regulator in the a-c. side of the 
machines as shown in Figs. 93 and 94. The regulator is con- 
nected with its secondaries in series with the a-c. lines and its 
primaries excited from the inverted machine. It is always 
preferable to connect the regulator between the inverted con- 
verter and the dynamometer board so that the instruments 
of the converter will not read the losses in the regulator. The 

196 



regulator takes the place of the booster used in the previous 
method, and is very satisfactory for supplying the PR losses. 

Starting the machine, checking the phase rotation, phasing 
in, and the other matters already described are repeated with 
this method. Always see that the regulator is set at the neutral 
point before phasing in, otherwise load will be thrown on when 
the switches are closed. For the no-load phase characteristic 
the regulator should be disconnected. 

Load is increased by turning the core of the regulator in 
the direction of boost, at the same time watching the ammeter 










Fig. 94 
TABLE CONNECTIONS FOR SYNCHRONOUS CONVERTER FEED BACK 



of machine Xo. 1. If the reading reverses from motor load, 
then No. 1 is running as a converter. If No. 1 does not reverse, 
turn the regulator in the opposite direction. This shows that 
the regulator is wrongly connected in reference to its markings. 
There is no necessity, however, to change connections. 

Using A-C. Loss Supply 

If instead of supplying the losses from a d-c. source of power, 
we connect an alternator across the a-c. lines (between the 
inverted converter and the regulator to avoid reading the losses 
in the regulator) in the preceding method the losses can be 
supplied at the a-c. end. When the alternator is large enough 
to start the converters, the wiring on the d-c. end is greatly 
simplified. The starting panel is omitted, and the shunt fields 
are connected according to the print of connections for the 
machine. Load is obtained by means of the regulator as before 
and the test carried out as already described. 

197 



If the alternator is too small to start the machines, the 
latter may be started from the d-c. side as before, and phased 
together. The alternator is then synchronized on the pair. 
If only one machine can be started by the alternator, bring it 
up to speed, then open all its circuits, and let it run by its own 
momentum, and quickly start the second machine. Take off 
the excitation from the alternator field, and then close the 
switches on the first machine. Excite the alternator field, and 
bring both machines up to speed, together. After the machines 
are once started they can be brought up to speed without 
excessive current being required. 

After the necessary heat runs have been taken and while 
the machine is still warm, the wiring should be removed and the 
high potential test applied. Hot drop on field spools, running 
light from the d-c. end, etc., should be taken as for other direct 
current machines. 

SPECIAL TESTS 

Special tests consist of d-c. and a-c. starting tests, core losses, 
saturation, impedance, voltage ratio at no load and full load. 
Voltage range curves at no load and full load will be taken on 
split pole machines. 

Saturation and impedance are taken in the same manner as 
for d-c. and a-c. generators, previously described. 

D-C. starting tests are taken with the machine running a*s 
a d-c. motor and wired to a d-c. machine of ample capacity to 
give satisfactory readings without an excessive fall in voltage. 
The main field of the converter should be excited at that cur- 
rent necessary for no load minimum input unless full field is 
specified. The current through the armature should be increased 
gradually until the armature begins to revolve and held constant 
at that value until the machine reaches synchronous speed. 
The elapsed time from start to synchronous speed should be 
recorded. This test should be repeated with higher values 
of armature current held and enough readings taken to plot a 
curve with amperes armature, as ordinates against time as 
abscissae so as to determine the current necessary to bring the 
converter to synchronous speed in one minute. 

A-C. starting tests are taken in the same manner as for a 
synchronous motor. 

The converter should be wired to an a-c. generator of suffi- 
cient capacity to start it without overloading. If transformers 
are needed, in order to get the correct voltage, they should be 
placed between the dynamometer board and the generator. 

Converters at starting from the a-c. end are similar to a 
transformer. The armature corresponds to the primary, and 
the field, having a large number of turns, corresponds to the 
secondary. Hence the induced volts on the field may be very 
high (often 3000 or 4000 volts). In all cases, therefore, the 
field connection must be broken in two or more places to keep 
this voltage within safe limits. A potential transformer and 
voltmeter should be connected across one or two spools in series, 

198 



for reading the induced volts field, and a note made on the 
record sheet as to the number of poles included in the reading. 

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Fig. 95 

EFFICIENCY AND LOSSES ON A 300 KW, 600 VOLT, 750 R.P.M., 

25 CYCLE, 3-PHASE SYNCHRONOUS CONVERTER 

Starting tests should be made from several different positions 
of the armature with respect to the field. A scale, corresponding 
to the distance between collector ring taps, should be laid off 
on the armature, divided into five equal parts. A point of 
reference is marked on the field, opposite to which the marked 

199 



positions of the armature are placed for the successive starts. 
These positions should be numbered and a sketch showing the 
numbering be made on the Record Sheet. 

Having brought point No. 1 opposite the reference point, 
the a-c. switches should be closed and a moderate field put 
on the alternator, sending about one-half normal full load 
current through the converter. Read volts and amperes in the 
various phases. As it will be impracticable to read all phases 
at once during the start, cut the ammeter into that phase which 
shows the highest current and the voltmeter across the phase 
which indicates the highest voltage, so as to get the maximum 
readings at the instant of starting. Increase the field of the 
generator until the armature begins to revolve, when volts 
and amperes input and induced volts on the field should be 
read. The voltage across the collector rings should then be 
held constant, until the converter reaches synchronism, the time 
required to reach this point from the start being noted. 

There are several methods of determining whether the ma- 
chine is in synchronism. One is, the induced volts field will fall 
to zero; another, the voltmeter across the armature will read a 
definite voltage, which would vary from a negative to a positive 
reading if the machine were below synchronism. 

Readings should be taken on all phases, of volts and amperes 
after the machine has reached synchronism. The machine should 
then be shut down, the armature brought to position No. 2 
and the test repeated. In this manner all five points should be 
taken. After these tests have been taken, the time required 
to bring converter to synchronism should be taken by throwing 
one-half voltage across the collector rings. 

Core Losses are taken with the converter running as a gener- 
ator and results recorded as given in previous chapters. A 
reading should be taken of the volts across the collector rings 
as a check on the no load ratio. Calculation Sheet 25 shows the 
results of a core loss taken by the motor core loss method. 

STANDARD EFFICIENCY TEST is made by the method of losses. 
Page 435 and Calculation Sheet 13 shows the method used in 
calculating the efficiency of a converter. See Fig. 95. 

COMPLETE TESTS consist of normal and overload heat runs 
and special tests. 

Other tests which may be called for on synchronous con- 
verters are: 

Compounding Test with Reactance 

When a converter is required automatically to deliver a con- 
stant direct voltage, with a load subject to sudden changes, a 
compound wound machine is used with a definite reactance 
inserted between the converter and the line. Such reactances 
must be tested with the machines for which they are designed. 
A constant voltage is possible, since an alternating current pas- 
sing through a reactance will increase the potential if leading, 
and decrease it if lagging. By adjusting the shunt field so that 
about 20 per cent lagging current flows at no load and the current 

200 



at full load leads slightly, the strength of the series field can be 
adjusted so as to give the same voltage at no load and full load. 
A compound wound converter, running with reactance, must be 
compounded like a direct current generator. Unless other specific 
instructions are issued in reference to compounding, hold con- 
stant the voltage of the alternator by which the converter 
is driven. Adjust the shunt field to give the correct no-load 
voltage, then, without touching the field rheostats, put on full 
load and read the direct volts. If the machine over-compounds, 
the series field is too great, and gives too much leading current. 
In this case a shunt must be adjusted across the terminals of 
the series winding to shunt a portion of the current. On this 
compounding test, all readings are taken and adjustments made 
as on a direct current generator without touching the field 
rheostats after the no-load adjustment is made. 

Pulsation Tests 

Since the torque of a converter need only be great enough 
to overcome that due to its own losses, it is very sensitive to 
changes in line conditions, viz., excessive line drop or speed 
changes of the driving unit. Line drop alone will start a machine 
pulsating, in many cases. Once started the pulsation generally 
increases rapidly, till the machine falls out of step or flashes 
over. To prevent pulsation, copper or brass bridges are located 
between the poles, which act as a short-circuited secondary 
and oppose sudden changes of the input armature current. 
Converters of new design are tested for pulsation by inserting a 
resistance per phase, between them and the driving alternator. 
The drop through this resistance corresponds to the line drop 
which will probably occur in practice. Usually 15 per cent 
drop is used. If two machines are tested together each machine 
would have 15 per cent drop between it and the driving alternator 
or there would be 30 per cent between the two machines as 
shown in Fig. 96. 

With the two machines running in synchronism self-excited 
and with the fields adjusted to give minimum input, observe 
the voltmeters on the d-c. end of the two machines. Any slight 
pulsation will be shown by these instruments at once. Hold 
the direct volts constant on one machine throughout the test. 
With one field held at minimum input value, reduce the field 
current in the other machine to about one-half minimum input 
value. If no pulsation is noted, take a full set of readings on 
both machines, then reduce the field current of the other machine 
to one-half minimum input value, and watch for pulsation on 
both machines which now take a heavy lagging current. Take 
a full set of readings under these conditions. Next adjust 
the field of the first machine again to the minimum input value, 
watch for pulsation and take readings. With this field held at 
minimum input, change the field of the other machine from 
its value at one-half minimum input to twice the minimum 
input value, observe and read. The other field is then brought 
up to twice normal value, readings are taken and the effect of 

201 



the heavy leading current in each machine noted. Leaving 
one field over excited, weaken the other field so as to get half 
minimum input, look for pulsation and take a full set of readings. 
Next adjust both fields for minimum current and raise and lower 
one field about once a second between the extreme values used 
above and repeat this test for the other machine. If no pulsation 
develops with the high line drop under these extreme conditions 
the machines are satisfactory. 






Dynamometer 
Board 

Alternator 

A A 




Resistance 




Resistance. 



Fig. 96 
CONNECTIONS FOR PULSATION TEST 



Input-Output Efficiency Test 

Input-output tests on small machines are made with 
the machine running as a converter, dead loaded on a 
water box. Larger machines are tested in pairs, one 
machine feeding back on the other with electrical loss supply. 
The machines are wired exactly in a similar manner to that 
used in a heat run (circulating current method) special atten- 
tion being given the wiring to see that no unbalancing occurs 
in either the a-c. or the d-c. circuits. On the machine running 
as a converter, wattmeters are connected in the a-c. end, between 
the converter and the transformers and preparation made for 
reading d-c. armature and field current and volts. If current 
transformers are used with the wattmeters, duplicate trans- 
formers must be used in the other phases of the machine to 
prevent unbalancing caused by the resistance and inductance 
of the transformers. With the machine running in synchronism 
at rated speed with zero load, and all meters connected, hold 
constant the alternating volts impressed on the converter 
and take careful readings of all instruments. Then read the 
current and volts in each phase, as a check on the wiring and 
balancing of all phases. Also carefully check all instruments 
for stray fields. Any instruments so affected must be protected 
by iron shields or their location changed. With full load, repeat 

202 



the test for stray fields, since any instrument affected will give 
misleading and erroneous results. With the no-load minimum 
input field current held constant, carefully read the a-c. input, 
as shown by the wattmeters, as a check on the no-load losses. 
As efficiency is usually guaranteed at \i, 3^2, Z A, 1> M and 1^ 
load, careful readings must be taken at these loads. Each time 
the load is changed, the converter field excitation must be 
changed to the minimum input value for that load. This is 
shown when the sum of the wattmeter readings is exactly equal 
to the kv-a. input. To obtain this condition every time usually 
requires several trials and considerable time, so that an efficiency 
test made in this way is more expensive than when made by 
the separate loss method. The likelihood of error is also greater. 

INVERTED CONVERTERS 

The speed of a converter, running from the a-c. side, is deter- 
mined by the line frequency. The same machine running as an 
inverted converter and delivering alternating current operates 
as a d-c. motor. Its speed depends upon the field excitation 
and load, and it will deliver a variable frequency, particularly 
if compound wound. When run inverted, a compound wound 
machine should have its series field almost, if not entirely, 
short-circuited when part of its load is inductive, since a lagging 
alternating current will weaken the field and increase the speed, 
sometimes causing a runaway. For this reason, care must 
always be taken when running a converter inverted, to see that 
sufficient field excitation has been obtained to prevent excessive 
speed, particularly when another machine is operated as a 
converter from the inverted machine. 

SPLIT POLE CONVERTERS 

The field poles of split pole converters consist of two or 
more separate and independent parts each equipped with 
its own field coil. The ratio of the converter is changed by 
varying the relative strengths of the main and auxiliary wind- 
ings. The transformers should never be connected delta primary 
with diametral secondary because of the harmonic current 
that may flow if this connection be used. The testing instruc- 
tions will include, besides the regular tests to be made, the volts 
to be held across the collector rings and the range through which 
the direct volts are to be varied by means of the auxiliary field. 

All preliminary tests are taken as for standard converters and 
the following tests are modified according to instructions below. 

Phase Characteristics 

Phase characteristics should be taken under three different 
conditions of excitation. 

NO-LOAD PHASE CHARACTERISTICS 

(a) Hold the direct volts constant and vary the main field 
with the regulating and compensating fields unexcited. 

(b) Hold the alternating volts specified in the testing 
instructions and with the main field only, find the main field 

203 



current for minimum input. (This may check with [a].) Set 
the main field rheostat to give minimum input current as just 
determined and vary the compensating field while using the 
regulating field to maintain the direct volts constant at the 
lowest limit. 

(c) Same as (b) except it is taken at the highest limit of 
direct volts. 

NOTE. — In case there is no compensating winding take 
curves corresponding to (b) and (c) by holding the direct volts 
constant with the regulating field while varying the main field. 

FULL LOAD PHASE CHARACTERISTICS 

The full load phase characteristics should be taken in the 
same manner as the no load, except that in all cases the current 
in the d-c. end should be held at the value necessary to give the 
rated output of the machine at the voltage on which the kilo- 
watt rating is based. 

Voltage Range Curves 

Voltage range curves are taken by holding the impressed 
volts constant and, with the main field rheostat set for minimum 
input current as found in (a) of the phase characteristics varying 
the current in the regulating field to obtain the specified range of 
direct voltage. Minimum input current must at all times be 
maintained by varying the compensating field. 

NOTE. — In case there is no compensating winding two 
curves should be taken. 

(1) Holding the main field rheostat constant. (2) Holding 
minimum input current by changing the main field rheostat. 

Curves are plotted with direct volts line as ordinates and 
amperes regulating field as abscissae. 

Similar curves should be obtained for full load conditions. 

Core Loss and Saturation 

Two core loss tests are required to cover the various condi- 
tions of operation. 

(1) Vary the direct volts by means of the main field only 
with the auxiliary field unexcited. This test is the same as for 
a standard machine. 

(2) Holding^ the alternating volts constant at the value 
specified in the instructions and with the main field rheostats 
in the position determined from (1) for obtaining the specified 
alternating volts, vary the regulating and compensating wind- 
ings to change the direct volts throughout the range. (It will 
be found necessary to vary the compensating winding in order 
to hold the specified alternating volts.) NOTE. — If there is no 
compensating winding, change the main field rheostat to hold 
the alternating volts constant. 

Saturation curves should be taken under the same conditions 
as core loss. 

204 



Running Light Readings 

Running light readings from the d-c. end should be taken 
under three different conditions. 

(a) Holding the specified alternating voltage using the 
main field onlv, and allowing the direct volts to come what they 
will. 

(b) Holding the minimum direct volts and the specified 
alternating volts by varying the regulating field, and varying 
the compensating field to obtain correct speed. 

(c) Taken in the same manner as (b) except at the maxi- 
mum direct volts. 

Heating Tests 

The heat runs should be made by holding the specified 
alternating voltage, varying the regulating field to obtain the 
desired direct voltage and adjusting the compensating winding 
to obtain minimum input. The main field rheostat should 
remain in the position found in obtaining the specified alternating 
voltage with normal current output and minimum current 
input when the compensating and regulating fields are unexcited. 
On those machines not equipped with compensating field, the 
main field must be varied to obtain minimum input. 

COMMUTATING POLE CONVERTERS 

The brushes of the commutating pole converter should be 
set on mechanical neutral for best commutation. This point is 
located by placing the armature bars, which are painted red, 
central with respect to a main pole, and then setting the brushes 
so that the center of the brush comes over the center of the red 
mark on the commutator as specified under "Commutating 
Pole Generators" in Chapter 7. It sometimes may be necessary 
to shift the brushes slightly forward to secure a falling voltage 
characteristic under load. 

When adjusting the commutating field on a converter, in 
order to determine whether it has the proper field strength, 
run the machine at full load or as near this value as possible, 
and take the drop from the pigtail of one brush to various 
points on the commutator under the brush. If the drop is 
the same to all points under the brush the adjustment is cor- 
rect, but if it is higher on the trailing side the commutating 
field is weak and if higher on the leading side, the field is too 
strong. 

Most commutating pole machines have a brush raising device 
to lift all except two pilot brushes from the commutator during 
the period of starting from the a-c. end. This device should be 
carefully examined to see that it operates satisfactorily, that 
it does not bind, that it raises all the brushes (except the pilot 
brushes) well off the commutator and that it allows all the 
brushes to make proper contact on the commutator with plenty 
of allowance for the wear of brushes. The pilot brushes are for 
the purpose of getting field on the machine and correcting 
reversed polarity if necessary. 

205 



Converters with A-C. Boosters 

Commutating pole converters which have an a-c. booster 
are equipped with an auxiliary shunt winding on the commutat- 
ing poles. The strength of this field is controlled by means 



'echanica.Ho 
Connected. 




Fi e. /a /?h&osta.t 



Fig. 97 

CONNECTIONS OF A-C. BOOSTER FIELD AND AUXILIARY SHUNT 

COMMUTATING FIELD WITH CONTROL FOR SYNCHRONOUS 

CONVERTER HAVING COMMUTATING POLES AND 

A-C. BOOSTER 

of a double-dial rheostat, which is mechanically connected 
and operated with the double-dial rheostat in the booster field, 
and an auxiliary resistance which is divided into steps that are 

206 



controlled by contactors. These contactors are set to operate 
at various loads thus changing the resistance in the shunt 
commutating field according to the load on the converter. 
(See Fig. 97.) The double dial rheostat takes care of any change 
in commutating field strength made necessary because of a 
change of the direct voltage of the converter. 

The contactor-controlled resistance is set for the maximum 
value of auxiliary field which will give good commutation at 
no load. The load is then increased to the maximum value which 
can be carried with good commutation at this field strength. 
The first contactor should be adjusted to close at this value 
(which will be about 40 per cent normal load) and the auxiliary 
field strength thus increased to the greatest value permissible 
without sparking. The load should then be increased to the 
maximum which will not cause sparking at this setting (which 
will be about 85 per cent normal load) and the second contactor 
adjusted to close at this point. The same operation should be 
repeated for the other two contactors which should be set to 
close at about 110 per cent and 130 per cent normal load. 

The only phase characteristics which need be taken on this 
type of machine are those with the booster field unexcited and 
are the same as those described for standard converters. 

The voltage range curves should be taken at no load and full 
load with the alternating volts held constant and are similar 
to those for split pole machines without compensating windings. 
The booster field is used in place of the regulating field. 

Core loss and saturation curves should be taken. 

(a) With the main field of the converter excited (booster 
not excited). 

(b) With the booster field excited and the converter not 
excited. 

The alternating and direct voltage of the converter should 
be read in each case. 

Other tests should be taken as previouslv described. 
MOTOR CONVERTERS 

A motor converter consists of a standard synchronous con- 
verter and an induction motor. The induction motor has a 
wound rotor with taps brought out to a set of common rings 
that take the place of the collector rings for both motor and 
converter. The voltage of the induction motor rotor is the 
alternating voltage of the converter. The advantage of the 
motor converter is that high tension (up to 13,000 volts) may be 
applied on the stator of the induction motor, the rotor delivering 
low voltage to the converter. Hence the intervening bank of 
transformers always necessary with a synchronous converter 
are not required. No reduction of power-factor is caused by the 
induction motor, since unity power-factor may be maintained 
with the motor converter by proper adjustment of the field of 
the synchronous converter. Caution should be observed when 
when staiting a motor converter to see that it does not exceed 
synchronous speed. This synchronous speed is always the syn- 
chronous speed of a machine having a number of poles equal to 
the sum of the number of poles on the synchronous converter 
and induction motor forming the motor-converter. 

207 



CHAPTER 12 

INDUCTION MOTORS 

The tests made on an Induction Motor either for Engineering 
information, or for checking guarantees may be divided as 
follows: Preliminary tests; commercial tests; heating tests; 
special tests; input-output tests. 

Preliminary test consists of air gap, resistance measure, and 
inspection as contained in the instructions in Chapters 3 and 4 
which should be carefully followed. Special measuring scales 
are used in taking the air gap of Induction Motors, as noted 
on page 83, Chapter 3. Great care should be used in taking 
both the stationary and revolving gap measurements. Ordinarily 
there should be as many points measured as there are openings 
in the end shield. On machines equipped with pedestal bearings 
at least eight equally spaced points should be taken. 

Resistance measure is generally made between terminals. 
On some machines the separate phases are each brought out to a 
terminal block. Whenever the resistance is measured per phase 
it should be clearly indicated on the record sheet. Quarter-phase 
machines are usually measured between terminals 1-3 and 2-4. 
Detailed descriptions of the apparatus and methods used in 
resistance measurements are given in Chapter 2. When a motor 
is delivered to test it bears a tag on which the resistance 
between terminals as measured by the Armature Department, 
is written. This value is generally accepted by the Testing 
Department and the machine need not be re-measured except 
when heat runs or special tests are to be made. All heat runs 
and special tests should be preceded by a resistance measurement 
taken when the machine is cold and a careful measurement by 
thermometer of the machine windings. 

Commercial Tests 

Commercial tests consist of preliminary tests, excitation 
readings, stationary impedance, and voltage ratio on Form M 
and Form P motors. The excitation readings consist of taking 
running light readings of volts and amperes with normal voltage 
impressed on the stator. The windings of phase wound rotors 
must be short circuited. Form L and Form P rotors should be 
short-circuited by means of the short-circuiting switch provided 
on the motor; Form M rotors should be short-circuited by con- 
necting the brush-holders together with a short cable. The 
brushes should be sanded to a good fit to reduce the -contact 
resistance as much as possible. In starting, the voltage should 
be applied gradually or in steps, the lowest being about one- 
quarter of the normal voltage. The majority of motors should 
start on one-fourth normal voltage with the rotor short-circuited. 
The voltage necessary to start must be recorded. The bearings 
must be watched carefully to detect any undue heating, especially 
in the case of high speed machines. End play must be tried out, 
both with and without voltage applied to the stator. A tachom- 
eter reading of speed should be taken and recorded to show 

208 



that the motor is running at the correct speed for the frequency 
of the circuit used, and also as a rough check on the frequency of 
the driving alternator. After the motor has been run for several 
minutes to show up any defects the readings of volts and amperes 
should be made and recorded. Care should be taken to detect 
any unbalancing in the voltage or current in the different 
phases. 

Stationary Impedance consists of taking readings of volts 
and amperes, at normal rated amperes, with the rotor short- 
circuited and blocked with the clamping device furnished for 
this purpose. On Form K motors, this value will be practically 
the same for any position of the rotor. On motors having 
phase wound rotors, it is necessary to vary the position of the 
rotor, with respect to the stator, in order to obtain the max- 
imum and minimum effects. Normal amperes is first obtained 
with any convenient position of the rotor, and the corresponding 
voltage is held constant during the shifting of the rotor position. 
This voltage is generally found to be about one-fifth of the 
rated voltage of the motor, a fact which will serve to detect 
any gross error which might be made in testing. On Form L 
motors, a reading must also be taken and recorded with the 
resistance in. Close attention must be given to current and volt- 
age balance on the different phases and much care must be used 
to avoid applying excessive currents and damaging the winding. 

Voltage ratio readings must be taken and recorded on all 
Form M and Form P motors. This consists in applying normal 
voltage to the stator winding, and measuring the voltage be- 
tween rings on the rotor winding, the rotor being open-circuited 
and held stationary. The primary exciting current must also 
be read and recorded. 

HEATING TESTS 

Heating tests generally taken on Induction Motors may be 
divided into actual load runs and equivalent load runs. 

ACTUAL LOAD RUNS 

The actual load runs may be sub-divided into normal load, 
overload, crane motor, and intermittent heat runs. They are 
usually made by belting or direct connecting the motor to a 
d-c. shop generator and holding normal voltage and the speci- 
fied current. The instructions in Chapter 4 relating to thermom- 
eters should be followed carefully. Readings should be taken 
every half hour on normal load runs, and every fifteen minutes 
on overload and crane motor runs. 

Crane motor heat runs are taken on motors designed for 
intermittent service and are generally made holding normal 
voltage and current for a half hour. In some cases the runs 
extend over a period of one hour. Readings should be taken 
every fifteen minutes. 

Intermittent heat runs are usually made according to instruc- 
tions from the Engineering Department. 

The Induction Generator method is sometimes employed in 
making load runs on Induction Motors. Two similar induction 

209 



motors are belted together and run in parallel from the same 
alternator which supplies the losses. See Fig. 98. In order to get 
full load in both machines, the diameter of the pulleys must 
differ by a percentage equal to double the full load per cent slip. 
In starting, the switches A are closed and the motor allowed 
to come up to speed, until the speed of the motor running as 
a generator is above synchronism. The alternator field is 
opened momentarily, while the switches B are closed. The 
circuit in the alternator field is then closed again, and full 
load current flows through the two machines. No changes in 




Fig. 98 
INDUCTION GENERATOR METHOD OF FEEDING BACK 



load can be made without changing the pulley ratio and it is 
absolutely necessary that this ratio be correct in order to obtain 
full load. 

Several modifications of this method are possible. The shafts 
of the two machines may be direct connected or belted together 
and one winding of the machine to act as the induction generator 
be separately excited with either alternating or direct current 
and the other winding connected to water boxes. In this 
method the induction generator cannot be a Form K machine. 

Another modification sometimes used is to wire the induction 
generator to the synchronous motor of a motor-generator set 
and load the set, the field of the synchronous motor being 
adjusted to supply the exciting current for the induction gener- 
ator. 

Slip readings should be taken during all heat runs as des- 
cribed on page 217. 

EQUIVALENT LOAD RUNS 

Equivalent load runs are generally made on large motors 
which it would be difficult to load on account of the large 
amount of power required. The heating due to iron losses is 
obtained by running the motor light at normal voltage until 
the temperatures of the various parts become constant, readings 
being taken and recorded as in actual load heat runs. The heat- 

210 



ing due to copper losses is obtained by running the motor under 
partial load at a voltage less than normal, and holding normal 
and overload currents. From the results obtained in these tests 
the temperatures which would be obtained under actual load con- 
ditions may be approximately determined. 

SPECIAL TESTS 

Special tests consist of excitation curves, impedance curves, 
slip curve, stationary torque test and starting tests. The excita- 
tion, impedance and slip curves are very important, since it is 
from these curves that the data are taken for the calculation of 
the characteristic curves of the induction motor. These curves 
are generally accompanied by torque tests and occasionally 
by starting tests. 

Excitation Curves consist of a series of readings of volts, 
amperes and watts, taken at different voltages when the motor 
is running light, the frequency of the applied voltage remaining 
constant. 

The motor should be so located that all conditions affecting 
its operation remain unchanged throughout the test. A solid 
foundation is necessary to prevent vibration at full speed. The 
driving alternator should be at least three-fourths of the kilo- 
watt capacity of the motor. It should be driven by an endless 
belt or by direct connection to its driving motor to avoid pulsa- 
tions in the instrument readings. The transformers and other 
apparatus must be connected so that the alternator is working 
under normal conditions, since satisfactory wattmeter readings 
cannot be obtained if the alternator is run too low on its satura- 
tion curve. Transformers when used must be well balanced 
and must not be forced beyond their voltage range. The alter- 
nator used should have a sine waveform. 

The testing table must be adapted for wattmeters. If the 
voltage be too high for direct reading on the wattmeters and 
voltmeters, multipliers or potential transformers must be con- 
nected between the points measured and the instrument; similarly, 
if the current be too high for direct reading, current transformers 
must be used in the wattmeter and ammeter circuits. On 
motors of less than 20 h.p., the potential lines must be attached 
on the generator side of the testing table, since, if they are 
attached to the motor side of the table or to the motor terminals, 
the exciting current of the potential transformers passes through 
the wattmeters. Although this current is small, it may be quite 
an appreciable percentage of the exciting current of a small 
motor, and the error involved may cause an abrupt break in 
the curve whenever a potential transformer ratio is changed. 
In the case of large motors, the exciting current of the potential 
transformer is so small in comparison with that of the motor, 
that the incidental errors are negligible. When multipliers are 
used the above precautions may be disregarded since they are 
non-inductive. On large motors the potential leads should be 
connected to the motor terminals to eliminate the line drop in 
switches and cables leading from the table to the motor. The 

211 



current leads to the wattmeters and ammeters should be twisted 
together throughout their length and should be free from sharp 
bends or loops. All connections must be bright and clean. 
The short-circuiting switches must always be closed when instru- 
ments are changed. On circuits of more than 500 volts all 
instruments must be discharged to eliminate static charge. 
Do not ground the secondary circuits of the potential trans- 
formers. The iron cases of oil-insulated potential transformers 
should be connected together and grounded. Each man should 
become thoroughly familiar with the characteristics and limi- 
tations of instruments and transformers as explained in detail 
in Chapter 2. 

In starting up, the same precautions should be observed 
as in commercial tests. After preliminary inspection of wiring, 
bearings, etc., the line switches of the testing table should be 
closed. Always see that the wattmeter short-circuiting switches 
are closed in starting, or whenever a change is made in the 
generator field excitation. The exciter field switch should be 
closed, and the voltage brought up gradually until the motor 
starts and reaches normal speed. The motor should then be 
inspected to see that it is operating normally. The amperes 
and volts in the different phases should be read, and any unbal- 
ancing discovered and a few check readings made with a dif- 
ferent set of instruments. The end play must be tried out, since 
defective end play may cause friction losses, which would render 
the excitation curves inaccurate. Small motors should be run 
about 1^ hours and larger ones at least 2J^ hours, in order to 
obtain constant friction, before beginning the curves. 

In taking an excitation curve on a quarter-phase motor 
both wattmeters read positive. However, in the case of a 
three-phase motor, one wattmeter reads negatively through the 
upper portion of the curve. It is, therefore, necessary to deter- 
mine the algebraic signs of the readings of both wattmeters 
before beginning the curve. Adjust the circuit so that both 
wattmeters show a positive deflection on the scale, then open 
one of the phases in which a wattmeter current coil is connected 
and observe the other instrument. If the needle drops off the 
scale below zero, the instrument reads negatively. If the needle 
drops to some value above zero the reading is positive. This 
process must then be repeated for determining the sign of the 
other wattmeter. 

In taking the data for the curves, the frequency of the 
alternator must be held constant. A value of about 125 per cent 
normal volts should be used for the first reading. Readings of 
volts, amperes, watts, and frequency must be made and recorded. 
The volts should then be decreased in steps to give 15 or 20 
points on the curve, down to a value of 10 or 15 per cent normal 
volts. At this point the motor becomes unstable. As readings 
are taken on the descending curve, the instrument with the 
negative sign will read less than the positive reading instrument, 
and its readings fall off more rapidly, becoming less and less until 
zero is reached and its sign changes. When it becomes positive 

212 



its current leads must be interchanged. The two most important 
points on the excitation curve are amperes and watts at normal 
voltage, and friction watts. These readings determine the 
core loss of the motor. Several readings only a few volts apart 



§4000 
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Fig. 99 

EXCITATION CURVES ON A 100 H.P., 6 POLE, 500 R.P.M., 440 VOLT, 
FORM M, 3-PHASE INDUCTION MOTOR 



should be taken on each side of normal voltage. The volts and 
amperes in the different phases should be read at normal volts, 
and at two or three other points in the curve as a check on the 
phase balance of the motor. These readings should be recorded. 

213 



As the lowest point on the curve is approached, a large number 
of readings should be taken, since it is from these readings 
that the friction watts of the motor are determined. In many 
cases hunting begins at low voltage. This causes the wattmeter 
needle to swing with a slow beat. Reliable readings can generally 
be obtained between beats but care must be used to avoid 
taking readings when the motor is accelerating or decelerating. 
Bad cases of hunting are not numerous. 

As a check on the three-phase curve, single- phase readings 
of several points around normal volts should be taken on the 
two phases in which the wattmeters are connected. Volts, 
amperes and watts should be read as in the three-phase curve, 
A few check readings should also be made with a different set 
of instruments. Before shutting down, curves should be plotted 
using volts as abscissae, and amperes and the algebraic sum of 
the wattmeter readings, as ordinates. The single-phase 
amperes are theoretically 1.73 times the three-phase or twice 
the quarter-phase amperes. Practically, however, the single- 
phase amperes have a value from 1.4 to 1.8 times the polyphase, 
for either three-phase or quarter-phase motors. The single- 
phase excitation watts generally come about 10 per cent higher 
than the polyphase on account of higher PR losses, the iron 
losses being practically the same whether the motor is running 
single-phase or polyphase. The temperature of the laminations 
should be recorded at the end of the test. 

The calculation of the excitation curves is done in the Cal- 
culating Room. The instrument readings are corrected by 
means of the calibration curves furnished by the Calibrating 
Laboratory. The data are then worked up, and the curves 
plotted. The data of a calculated excitation test are shown on 
Calculation Sheet No. 16. Fig. 99 shows a typical set of excita- 
tion curves, plotted from this data. 

Impedance Curves consist of a series of readings of volts, 
amperes and watts, taken at different values of current, when 
the rotor is blocked and short-circuited, the frequency of the 
applied voltage being constant. The test table arrangement 
is the same as that for the excitation curve. 

The rotor of a squirrel cage (Form K) motor is a sym- 
metrical bar winding; therefore, the impedance of the motor 
is practically the same for any position of the rotor relative 
to the stator. In Forms L, M, and P motors having 
phase-wound rotors the impedance varies with different posi- 
tions of the rotor relative to the stator. It is therefore neces- 
sary to determine the rotor positions at which the impedance is 
maximum and minimum so that the rotor may be blocked on 
an average position for the impedance curves. For accomplish- 
ing this, a position curve is taken. Before taking the position 
and impedance curves, the rotor must be short-circuited. This 
is accomplished in Forms L and P motors by means of 
the short-circuiting switch and in the Form M motor either by a 
short cable connected directly to the collector rings, or by short- 
circuiting the brush-holders, using metallic brushes in order to 
reduce the contact resistance to a minimum. 

214 



Position Curve. In taking the position curve, an angular 
distance should be marked off on the end shield, equivalent 
to one-half of a pole pitch for quarter-phase motors, or two 
thirds of a pole pitch for three-phase motors. This space should 
then be pointed off into about ten equal parts. A pointer 
should be attached to the motor shaft or pulley so that its 
outer end will pass over the division marks. The pointer is first 
set on position Xo. 1 and the rotor blocked so that it cannot 
move from that position. The switches should then be closed 



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Fig. 100 
POSITION CURVE ON A 100 H.P., 500 R.P.M., 25 CYCLE, 
440 VOLT, FORM M, 3-PHASE INDUCTION MOTOR 
(Test Taken at 63 Volts) 
and the impressed voltage increased gradually, until a value of 
about normal amperes is obtained. Volts and amperes on all 
three phases should be read and recorded to make certain that 
there is no unbalancing on the different phases. Holding the 
same volts as in position Xo. 1 the rotor should be turned until 
the pointer is over position Xo. 2 where the amperes should 
again be read. This is repeated on each of the succeeding posi- 
tion?. A curve should then be plotted between position number 
as abscissae, and amperes as ordinates (when this curve is 
plotted for Engineering Data, the ordinates used are the 
amperes at normal volts found by multiplying by the ratio 

,t \ ■ . ). The rotor is blocked for the Impedance 

-oltage used in test/ * 

Curve on the position which gives an average value of current. 

See Fig. 100 and Calculation Sheet 17. 

215 



fe 



Impedance Curve 

Having blocked the rotor in any convenient position, in the 
case of a squirrel cage rotor, or on the average position as shown 



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Fig. 101 

IMPEDANCE CURVE ON A 100 H.P., 500 R.P.M., 25 CYCLE, 440 VOLT, 

FORM M, 3-PHASE INDUCTION MOTOR 



by the position curve in the case of a phase-wound rotor, the 
impedance curve may now be taken. The readings of volts, 
amperes and watts should be taken beginning at the lower part 

216 



of the curve, the current readings increasing in steps until a 
a value of 150 per cent normal amperes is reached. Up to this 
point about 12 or 15 readings should be taken, special care being 
used to get several good readings at and near normal amperes. 
Above the 150 per cent normal ampere point the wattmeter read- 
ings may be discontinued, the curve of volts and amperes alone 
being extended with several points, to a value of 300 per cent 
normal amperes. Great care must be used not to overheat the 
motor windings. A set of phase-balance readings should be 
taken at normal amperes. Single-phase check readings should 
be made on the two phases in which the wattmeters are con- 
nected, at a voltage equal to that necessary to obtain normal 
amperes on the three-phase curve. The single-phase impedance 

amperes should be times the three-phase at the same volt- 
age. The single-phase impedance watts should be Y2 the three- 
phase at the same voltage. In taking the curve data, the cur- 
rent should not be held on the motor any longer than is neces- 
sary to secure a reading. After each reading the exciter switch 
should be opened until ready to take the next reading, thus 
keeping the temperature of the motor more nearly uniform. 
Final temperatures of the rotor conductors should be recorded. 

Curves should be plotted using volts as abscissae, with 
amperes and the algebraic sum of the watts as ordinates. The 
volt-ampere curve is a straight line, curving slightly upward 
on the higher values. Single-phase amperes are practically 
equal to the polyphase, in the case of quarter-phase motors; or 
about 86 per cent of the polyphase for three-phase motors. 
Single-phase watts should be about one-half of the polyphase, 
for either quarter-phase or three-phase motors. 

The calculation of the impedance curves is done in the 
Calculating Room. The data of a calculated impedance test 
is shown on Calculation Sheet No. 19. Fig, 101 shows a typical 
set of impedance curves, plotted from the data given there. 

Slip Curve. There are several methods employed by the 
Testing Department for measuring the slip of induction motors, 
among which the following are the more important: First, by 
means of a slip indicator; second, by means of an arc lamp 
and revolving disk; third, by means of a voltmeter; and fourth, 
by means of a revolution counter. 

The method employing the slip indicator is the one most 
commonly used. The construction and operation of this instru- 
ment are described in detail in Chapter 2, page 27. 

The arc light and revolving disk method is a good one but 
it requires more time to set up the apparatus than does the slip 
indicator method. A disk (see Fig. 102) having as many white 
and as many black sectors as there are poles on the motor, is 
attached to the shaft of the motor, so that it revolves with it. 
This disk is illuminated by an alternating current arc lamp which 
is operated from the same alternator as the motor. Assume 
a six pole 60 cycle motor running at the synchronous speed 
of 1200 r.p.m. or 20 revolutions per second. Then 20X6 or 120 

217 



black sectors pass a stationary point on the circumference of the 
disk, in one second. As the frequency is 60 cycles, the arc lamp 
will give 120 maximum illuminations per second. The black 
sectors, would therefore appear to be stationary. Practically, 
the induction motor cannot run at synchronous speed, and the 
slip, at each maximum illumination will cause each black sector 
to lie a small angle behind that seen by the previous illumination. 
These successive differences in position appear as sectors 
rotating backwards, which can be followed by the eye. The 
difference between the actual speed and the synchronous speed 
of the motor can be counted. 




Fig. 102 
DISK FOR MEASURING SLIP OF SIX-POLE MOTOR 



The voltmeter method affords a very accurate and con- 
venient scheme for measuring the slip of motors having collector 
rings. The alternating voltage drop across the brushes is read 
by means of a low reading d-c. voltmeter. Every time the 
rotor slips an angular distance of two poles behind the synchro- 
nous revolving field of the stator, a complete voltage cycle is 
generated in the rotor winding. The d-c. voltmeter will be 
deflected in a positive direction every alternate half wave or 
once everjr cycle. Therefore, by counting the number of positive 
beats per minute of the voltmeter and dividing this value by 
one half the number of poles, the slip of the motor is obtained 
in revolutions per minute. 

The method employing^ a revolution counter is generally 
used in the case of high speed machines where it is not possible 
to measure the slip by any of the methods above described. It 
consists in reading the number of revolutions of the rotor for 
a known interval of time by means of a revolution counter. The 
difference between the speed thus measured, and the synchro- 
nous speed, gives the slip of the motor in rev. per min. Several 
readings should be taken and averaged, when this method is 
employed. 

In all of the foregoing methods for taking slip, it is very neces- 
sary that the load and impressed voltage on the motor, and the 

218 



frequency of the driving alternator, remain constant while the 
readings are taken and in each case the speed must be checked with 
a speed counter. 

Slip readings must always accompany heat runs. When 
special tests are made, a slip curve should always be taken. 
This curve must have readings at no load, and at 50, 75, 100 







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m 120 160 


» 200 220 



Fig. 103 

SLIP CURVE ON A 100 H.P., 500 R.P.M., 25 CYCLE, 440 VOLT, 

FORM M, 3-PHASE INDUCTION MOTOR 



and 125 per cent of normal load amperes. Sometimes it is not 
possible to hold normal voltage on the motor on account of the 
large amount of power necessary. In such cases the highest 
obtainable voltage should be held and the voltage and current 
should be reduced from normal in the same proportion. The 
motor should always be heated to its normal running tempera- 
ture at the time the slip readings are taken. All readings of 
volts, amperes, and slip must be recorded. A typical calculation 

219 



of a slip curve may be found on Calculation Sheet No. 18. 
Fig. 103 shows a slip curve plotted from the data given. 

Stationary Torque Tests. Two methods are employed for 
measuring stationary torque, one in which a spring balance is used, 
the other in which a special torque indicator is used, each in con- 
nection with a lever arm attached to the shaft. The first method 
applies to motors having squirrel cage rotors, in which the torque 
is practically constant for varying positions of the rotor relative 
to the stator. The second method is used on motors having 
phase-wound rotors, in which the torque is not constant for all 
positions of the rotor. 




T S 

Fig. 104 
MEASUREMENT OF TORQUE BY MEANS OF SPRING BALANCE 



In the first method the lever is clamped to the pulley or 
shaft as shown in Fig. 104. The size and length of the lever 
depends on the rating of the motor, the lever and spring balance 
being chosen to give a maximum reading at about % of the 

capacity of the balance used. Torque at 1 ft. radius = — 

In estimating the length of lever needed, allowance should be 
made for at least 175 per cent of full load torque. The balance and 
length of lever L should be chosen to make ( W-\- F-\- T) (see below) 
equal to at least twice (W+F). Let the point of attachment to 
the lever be at X. Then XF = the length of the lever arm. On 
the frame of the motor, a mark should be made at M, correspond- 
ing to the position of the pointer P, when the distances TX and 
SY are equal. If the weight of the lever is not sufficient to over- 
come the friction of the bearings and allow it to turn downward 
of its own weight, attach the additional weight, W. Open all 
line switches, thus doing away with any torque effect resulting 
from residual magnetism of the alternator field. By means of 
a suitable windlass, raise the lever slowly, pulling vertically 
on the spring balance H. As the pointer passes the mark M 
read the tension as indicated by the balance. Call this reading 
(W-{-F), W being the force due to the weight of the lever and F 

220 



the force due to bearing friction of the motor. Raise the lever 
until the pointer is some distance beyond M, then lower it slowly 
allowing the force of gravity to pull it toward the floor. When 
the pointer passes the mark M, the spring balance should again 
be read. Call this reading (W — F). The lever should be moved 
as steadily as possible, otherwise the tension indicated by the 
spring balance will fluctuate. Several readings should be taken 
as described above. 

Now close the line switches and bring up the line current 
gradually to a value of 200 per cent normal amperes. In so 
doing, watch the motor carefully to see that it does not tend to 
turn in the wrong direction. Take readings in the same manner 
as that just described. Call the reading taken as the lever is 
raised (W+F+T) t and that taken as it is lowered (W—F+T), 
T being the force due to the stationary torque of the motor. 
The readings should be recorded as follows: 

Volts Amperes (W+F) (W-F) (W+F+T) (W-F+T) T. 
Solving for the value of T, and knowing the length of the lever 
arm in feet, L, the stationary torque is calculated from the formula 

Stations To rqU e=(^L^y Xi xr 

Care must be taken to see that the motor does not overheat. 
To get reliable readings the frequencv of the alternator must 
be held constant. If any variation of (W+F+T) and W-F+T) 
should occur with change of rotor position, the maximum and 
minimum values should be recorded. As a check on the readings 
taken, the lever should be loosened and the rotor turned to a 
different position relative to the stator. Here the lever should be 
again clamped to the shaft or pulleys and readings of (W+F+T) 
and (W—F+ T) taken. This should be repeated for several dif- 
ferent positions. The temperature of the rotor conductors must 
be taken and recorded at the end of the test. 

The second method of taking torque applies to Forms L, M 
and P motors having phase- wound rotors. The data is taken by 
mean of a special torque indicator described in detail in Chapter 2, 
page 29. The indicator must be fastened to the lever arm so 
that the rope pulls vertically upward on the instrument. The 
cord used should have no tendency to twist when decreasing 
in length. In taking the torque cards, the diagram need cover 
but one pole-phase, to represent a complete torque cycle of the 
motor. The purpose of the indicator is to show the minimum 
torque effect exerted by the motor. 

On Form L motors two torque cards should be taken; one 
with the secondary starting resistance in, the other with it all 
cut out. A current of one-half normal amperes should be held 
for the reading with resistance in. Normal amperes should 
be held for the card taken with the resistance cut out. The 
motor should be carefully watched to see that the secondary 
resistance does not become too hot. Temperatures of the rotor 
must be recorded. 

On Form M and Form P motors, torque cards are generally 
taken with different values of secondary resistance. Sometimes 

221 



the secondary resistance is changed by changing the leads to 
the grids, and often by means of a controller. Whenever the 
test is made with a controller, a torque card should be taken 
for each controller position. The current held for these cards 
should be as near normal as the heating of the motor and grids 
will permit. The grids must not be allowed to become too hot, 
since this would lead to unreliable results, on account of the 



600 















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Fig. 105 

CHARACTERISTIC CURVES OF A 100 H.P., 500 R.P.M., 25 CYCLE, 

440 VOLT, FORM M, 3-PHASE INDUCTION MOTOR 



rapid change in resistance with change of temperature. Tempera- 
tures of the rotor and grids should be recorded for each card 
taken. Calculation Sheet 22 shows the results of this test 

Starting tests are closely associated with the torque tests 
just described. They are generally taken according to instruc- 
tions given by the Engineering Department. 

Characteristic curves of the Induction Motor are calculated 
from the data obtained from the special tests. The data of a 
calculation are shown on pages 439 to 445 and Calculation 
Sheets 20 and 21. The corresponding characteristic curves are 
given in Fig. 105. 

The data used in the calculation are taken from the excitation 
curves (Fig. 99), the Impedance Curves (Fig. 101) and the slip 
curve (Fig. 103). 

222 



COMPLETE TESTS consist of normal and overload heat runs 
and special tests. 

SPECIAL OVERLOAD HEAT RUN consists of bringing the machine 
to normal load temperatures, then applying 50% overload for 
two hours and recording temperatures, then applying 25% over- 
load until constant temperatures are reached and recording 
temperatures. 

LONG COMMERCIAL TEST consists of taking equivalent load 
heat runs, readings of excitation and stationary impedance. 

GENERAL TESTS consist of taking excitation and impedance 
tests with wattmeters, single-phase, at points near normal volt- 
age and normal current respectively. 




Fig. 106 

DIAGRAM OF APPARATUS USED IN TAKING INPUT-OUTPUT BY 

THE STRING BRAKE METHOD 



STANDARD EFFICIENCY AND POWER-FACTOR TESTS consist 
of calculating from general or special tests the efficiency and 
power-factor at any load. 

INPUT-OUTPUT "EFFICIENCY AND POWER- FACTOR TESTS con- 
sist of determining the efficiency and power-factor directly by the 
input-output method with wattmeters. 

They can be made either by the "String Brake" or "Electri- 
cal Load" methods. Neither of these methods is particularly 
accurate nor are they recommended. In certain cases, however, 
these tests are made on Induction Motors. 

String Brake Method 

In Fig. 106 L is a lever or scale beam suspended at the point 
,Y. From T the small platform A is suspended, on which cali- 
brated weights are placed. P is a flat faced pulley on the shaft 
of the motor running in the direction shown by the arrow, 
i.e., toward the lever L. One end of a small rope is attached 
at B, which is wound one or more times around the pulley. 
The other end is made fast to a spring balance G. A strip 
bearing a mark is located at K so that when the point of the 
lever L comes opposite to the mark, the lever is in a horizontal 
position at an angle of 90 degrees to the force exerted by the 
pulley. 

223 



Since the stress along a rope is transmitted through its 
center, adjust the brake until the points M and N are a distance 
apart equal to the diameter of the pulley plus the diameter 
of the rope, one-half the diameter of the rope being added to 
each side of the pulley. This adjustment must be carefully 
made and care taken to see that nothing moves to throw the 
brake out of line or proper adjustment. When ready, slip one 
turn of the rope off the pulley but leave it attached at B and G, 
then balance the lever until the pointer on the end comes to rest 
at the mark K. This balancing of L must be repeated each time 
the rope is changed. 

The motor should be run light for at least one hour before 
the test proper is commenced, so that friction may become 
constant. Since speed is one of the important factors in the 
output of the motor it should be taken very carefully. 

Running light readings should now be taken on the motor. 
The voltage impressed on the motor should be held constant 
as well as the impressed frequency. Attach a small weight 
to the spring balance to give enough tension on the spring for 
a reading on the balance of a quarter or half a pound. This 
"no load" scale reading must be recorded and subtracted 
from all subsequent readings taken. 

Put a small weight on A and pull up on the spring balance 
G until the pointer on lever L reaches K. Then when the motor 
volts and speed of the generator are normal and all meters 
are steady, read and record volts, amperes, watts, weights on 
A, spring balance reading and speed given by the tachometer. 
A reading should also be taken of the slip. Add more weight 
to A and take another reading, continuing in this manner until 
the breakdown load of the motor is reached. For an induc- 
tion motor the readings should be recorded in the following 
manner: 



Volts Amps. 



+ Watts -Watts 



Weight Tension 
on A on balance 



Speed 
Slip of 
Motor 



A rope of small diameter gives better results than a larger 
one, even though it may require more time to make the tests 
on account of having to renew it more frequently. On motors 
up to 20 h.p. a }/i in. oiled hemp rope is best and a Y2 in. rope 
can be used up to 50 h.p. The rope will last longer, usually, 
if doubled and two strands used in parallel. The rope turns 
around the pulley should all lie closely and evenly together 
on the face of the pulley. The tension read on the balance 
G will vary with the temperature of the rope and may differ 
widely with different loads. 

The additional weight put on A each time should be such 
as to give from fifteen to twenty readings between no load 
and breakdown. 

When the breakdown point has been reached and complete 
readings taken and recorded the diameter of the pulley should 
be carefully measured. 

224 



(Weight on A ) — (tension on balance) -("no load ' ' reading on 

balance) = actual load in pounds = P. 

(Normal speed) —(slip) = actual speed of motor. 

R = (Radius of pulley in inches) +(3^ diameter of rope.) 

5 = Speed in revolutions per minute. 

_, , . Watts 

Power-iactor = 77- 



Then H.P. 



l-RXPXS 



Volts Xamps. 



12X33,000 

_™ . H.P. output X746 

Efficiency = =r— — : 

\\ atts input 

When making any special test, the tester should see that 

the tests check among themselves before handing them in. 

Efficiency by the "Electrical Load" Method 

Consider Fig. 107; let if be the motor and L the load machine. 
This should be of about an equal capacity and be belted to 



rfies/stonce 




To Measuring 
Instruments 
and l/'ne 



To Water Box 
orSu/tati/e Motor 



Source of Current 

Fig. 107 

CONNECTIONS FOR MEASURING INPUT-OUTPUT BY 

"ELECTRICAL LOAD" 



the motor M. It should be a direct current machine, and 
must be separately excited from a suitable source of energy. 

To take the efficiency test, connect M so that the total 
input can be obtained. Separately excite the field of L, con- 
necting an ammeter and a variable resistance in circuit. Connect 
the armature of L to a water-box or a motor the load of which 
can be varied, placing an ammeter in the circuit and a voltmeter 
across the brush terminals. If the test involves a considerable 
range of speeds, run M over that range, and hold the field current 
of L constant, its value being such that the speeds or loads 
required for M can be obtained. 

Having made the necessary connections, etc., keep the field 
current of L constant at its predetermined values. Vary the 
load on L by changing the water resistance or the load on the 

225 



motor to which it is connected, to suit the testing conditions 
required on M. The efficiency of M may be required for a 
series of speeds or loads. Read the input and speed of M, 
and the volts and amperes of L, keeping the field of L constant 
and noting its value. The "counter torque" must now be 
obtained to complete the calculations. 

To obtain this, disconnect M, connect L to a source of 
current which can be varied so as to give L different speeds, 
keeping L separately excited. Run L as a motor driving M, 
keeping the field current of L constant with the same value it 
had when L was used as a generator. 

Vary the speed of L so that the speed of M can be varied 
slightly below its previous minimum speed to slightly above 
its maximum speed. Take a number of readings at varying 
speeds, reading volts and amperes input of L and speeds of L 
and M. If the electrical efficiency alone is desired (case A), 
sufficient readings have been taken. If the commercial efficiency 
is desired (Case B), take off the belt from L, and run it light 
as a motor. Vary its speed from slightly below to slightly 
above the speeds used before when running as a motor, and 
take a number of readings at different speeds, reading volts 
and amperes input and speed, separately exciting L, with the 
same current used in the two previous cases. The necessary 
readings are now complete for calculating the efficiency. 

Case A 

Let Wm be the total input of M. 

Let Wl be the product of volts and amperes read for L. 

Let Fm be M's friction, windage, etc. 

Let Fl be L's friction, windage, etc. 

Divide the belt friction equally between L and M including 
this in Fm and F/. 

Let R be the hot resistance of Us armature, which must be 
measured. 

Let / be the current in L's armature. 

Then electrical efficiency = ==. where CT is the 

mechanical losses in L and M and the belt loss. 
Case B 

Commercial efficiency = == where CT is the 

mechanical losses of L including belt loss. 

In running the counter torque curves, the field of L must 
be held constant throughout, and readings must not be taken 
when accelerating. 

HIGH POTENTIAL TESTS should be taken on all induction 
motors as called for in the Engineering Instructions. 



226 



CHAPTER 13 

STEAM TURBINES 

Since the horizontal type of turbine has almost entirely sup- 
planted the vertical type, the following instructions and illustra- 
tions will refer principally to the horizontal machines. How- 
ever, the work of operating and testing is practically the same 
for both types, except in certain features which will be dealt 
with separately, and the instructions may, in general, be con- 
sidered as applying to both types. 

Nomenclature 

Due to the radical differences in construction of the steam 
turbine from that of any other prime mover, there are many 
parts more or less unfamiliar to the average engineer. To 
secure uniformity in the designation of parts, thus avoiding 
any uncertainty and unnecessary cTelay, Figs. 108 and 109 should 
be carefully studied until thoroughly familiar. 

The number of stages of both vertical and horizontal machines 
is indicated by the following form letters. 



Xo. of 
Stages 


Vertical 


Horizontal 


Xo. of 
Stages 


Vertical 


Horizontal 


1 




A 


7 


M 


P 


2 


B 


C 


8 


Q 


R 


3 


D 


E 


9 


S 


T 


4 


F 


G 


10 


u 


W 


5 


H 


J 


11 




AA 


6 


K 


L 


12 


BB 


CC 



Generators are indicated thus: 



Type 


Form 


ATB Vertical 
ATB Horizontal 
CC Horizontal 


T 
HT 

T 



Tests 

Tests on a steam turbine may be divided into two classes, 
Commercial Tests and Special Tests. 

For commercial tests the turbine is assembled in Building 
No. 60, and is operated non-condensing at practically no load, 
and without regard to any definite steam pressure or super- 
heat. The tests consist of dynamic balance, adjustment of 
operating and emergency governors, and the inspection of the 

227 




Fig. 108 
VERTICAL TURBINE AND GENERATOR 



228 



PARTS OF VERTICAL CURTIS TURBINE AND 
GENERATOR (See Fig. 108) 

1 Condenser base 

2 Intermediate holder 

3 Turbine head 

4 Steam chest 

5 First stage nozzle 

6 Operating valve 

7 Generator stool 

8 Coupling 

9 Ends of field coils 

10 Field core 

11 Armature core 

12 Armature spider 

13 Armature coils 

14 Coil supporting rings 

15 Ventilating fan 

16 Top bearing bracket 

17 Top bearing 

18 Collector and brush-holder 

19 Operating governor 

20 Governor dome 

21 Governor beam 

21 Governor beam 

22 Governor rod 

23 Governor dome stool 

24 Ventilating hood 

25 Mid bearing cap 

26 Mid bearing 

27 Pilot valve chest 

28 Hydraulic cylinder 

29 Head end carbon packing rings 

30 First stage wheel 

31 Exhaust end carbon packing rings 

32 Packing ring dome 

33 Guide bearing 

34 Step bearing 

35 Intermediate buckets 

36 Nozzle diaphragm 

37 Cam shaft 

38 Emergency governor 

39 Shaft 

40 Field spider 



229 




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231 



unit, complete with its generator, for proper assembly and 
satisfactory mechanical and electrical operation. All machines 
must be assembled complete in all details and pass inspection 
before leaving the factory. 

Special Tests include in addition to commercial tests, steam 
consumption and efficiency tests. For this purpose machines 
are set up and run in Building No. 61, where provision is made 
for obtaining any desired steam pressure, superheat, and vacuum 
and for loading on water boxes. 

Steam, Exhaust and Oil Piping 

For the commercial tests in Building No. 60, steam is pipe 
from the Power Station in Building No. 61 through two 12 inch 
mains. These mains enter Building No. 60 at the front of the 
building and are carried overhead to the testing section. One 
main runs along the test gallery and then enters a duct where it 
connects with the other main which has been brought down on 
posts nearer the side of the building. Through the duct the 
main is brought around to the front of the test floor. Taps are 
made to the main at each test stand. At the points where the 
steam mains enter the test, are located in each main electrically 
operated valves. The valves are provided with controlling 
switches located at easily accessible points about the test floor 
and gallery. These valves are for emergency use only. It must 
be remembered that they control the steam for all pressure pumps 
as well as steam for the turbines, hence must be used only as a 
last resort. All men should become familiar with their location 
and method of operation. Two main exhaust lines are provided. 
They run under the gallery and across the test floor at the upper 
end of the test. The upper main leads to the atmosphere, and 
also to the factory heating system. This main may be connected 
directly or through lateral sub-mains to any stand on the test 
floor. 

The lower main leads to a 6700 sq. ft. Worthington con- 
denser located in a pit under the gallery, and is available for 
use on about half of the test stands. Machines to be loaded 
are connected to this main, but through a header provided with 
valves by means of which the machine may also be connected to 
the atmospheric main. The exhaust headers are also provided 
with drains, and these may be connected with the condenser or 
the atmosphere as occasion demands. 

There are four pressure oil lines. One line known as the 
"small accumulator" line, has connections at every stand on 
the test floor. The small accumulator is located in the small 
pump pit and maintains a pressure of about 125 lb. per sq. 
in. The object of the accumulator is to reduce the pulsation 
in the line due to the stroke of the pumps, and also to hold a 
small reserve of oil under pressure long enough to allow a change 
of pumps in case of a break down. This pressure line is used 
on the oiling system and the governor valve hydraulic mecha- 
nism of all vertical machines, and on the oiling system of hori- 
zontal machines not provided with an auxiliary steam pump 

232 



. 



until such time as they may be ready to have their gear pumps 
assembled. 

The other three lines can be connected only to the testing 
stands on that section of the floor used for vertical machines. 
Of these lines, one is the "step" or "large accumulator" line, 
and supplies oil at a pressure of 1150 lb. per sq. in. for use on 
step bearings. The large accumulator is located in a separate 
pit with the step pumps, and is used for the same purpose as 
the small accumulator on the low pressure line. 

The remaining two lines are known as the " variable pressure " 
lines and are not connected to an accumulator, but by means 
of adjustable relief valves may be operated at any pressure 
desired. They may be used on water pressure if necessary to 
supply a water step bearing. All oil is drained back into a 
common supply tank located in one of the pump pits. All 
steam piping is under the supervision of one man, not a test 
man, who will take care of the opening and closing of all steam 
valves, except the valve nearest the machines under test. This 
last valve, that is, the valve controlling a single machine, will 
be operated by the man in charge of the tests on the machine. 
The test man will be responsible for the exhaust valves. 

The oil system, pumps and condensers are in charge of a 
pump man who will take care of all valves except those con- 
necting directly with the machines under test. 

Instruments 

With the exception of electrical instruments, transformers, 
and thermometers, all instruments used on turbine test, such as 
gauges, tachometers, air-measuring devices, etc., are kept in the 
turbine test supply cupboards in charge of the pumpman. They 
are given out on receipt in the same way as instruments at the 
Instrument Rooms. 

Special Instructions 

In addition to instructions given in this book, there will 
be found further written instructions in a folder on the shelf 
near the door of the turbine test office. These written instruc- 
tions take up some matters more in detail than would be desir- 
able here, and also give special instructions which are subject 
to change at intervals. Hence this folder should be consulted 
frequently. 

Preparing Machines for Test 

When a machine is first delivered to the Testing Depart- 
ment the turbine only is assembled and made ready for wheel 
balance. Considering a horizontal machine, the first step is to 
test out the cooling coils in the bearings for water leaks. See 
Fig.110. 

Water should be turned on and the oil drains from the bear- 
ings watched for indications of water which might leak through 
inside the bearings. 

233 




Fig. 110 

BEARING (WATER COOLED, HORIZONTAL TURBINES) 

1 Top half bearing 

2 Bottom half bearing 

3 Cooling coil 

4 Retaining clip for (3) 

5 Terminal block for (3) 

6 Oil feed inlet 

7 Oil guard for bearing shell 

8 End packing ring for bearing standard 

9 Oil deflector ring 



234 




Fig. Ill 



ADJUSTABLE REDUCING BAFFLER FOR REGULATING 
BEARING PRESSURES (HORIZONTAL TURBINES) 



1 Reducing baffler frame 

2 Reducing baffler plug 

3 Stuffing gland for (1) 

4 Nut for (3) 



5 Handwheel for (2) 

6 Support for packing 

7 Nut for (5) 

8 Pipe plug for (1) 



Any trace of water escaping into the oiling system should be 
reported at once, and corrected before proceeding further. If, 
however, there is no apparent leakage, the oil tank may be 
filled, or oil turned on from the low pressure test system. It 
is only on such machines as are not equipped with an auxiliary 
steam pump that the department oil system is used, and then 
only during balance work. The auxiliary steam pump, when 
used, must be provided with a lubricator which must be in 
operation whenever the pump is working. 

With pressure on the oiling system, look over the machine 
for leaks in the piping, and if all right, set the pressure at 15 
to 20 pounds by means of the adjustable baffler shown in Fig. 
111. 

Before turning steam into a machine each bearing must be 
inspected for oil flow. It is not enough to inspect the pressure 
gauge only, as one bearing may have its flow entirely cut off 
and still the gauge would read properly. The proper amount 
of cooling water to be used on the bearings is better ascertained 
after the machine has been run at normal speed a short time. 
The quantity, which is adjustable at each bearing, should be 
such that the water is lukewarm as it leaves the bearing. Using 
a larger quantity is wasteful, and unnecessary. 

The oiling system of the vertical machine differs from that 
of the horizontal machine in several respects. Oil pressure is 
always supplied from the shop system, and the flow to each 

235 



S/yM '//o/6 » 
£ear//?y 




Fig. 112 
STEP BEARING 



236 



DETAILS OF STEP BEARING (Fig. 112) 

1 Collar for supporting rotor when removing bearing 

2 Step guide bearing with holding bolts and keepers 

3 Guide pin 

4 Key for driving (5), with screws 

5 Revolving step plate 

6 Plug for (5) 

7 Bolts and keepers for fastening (5) to shaft 

8 Stationary step plate 

9 Bushing and pin for (8) 

10 Key for driving (8), with screws 

11 Step bearing head with bolts 

12 Adjusting screw 

13 Threaded bushing and pin for step bearing head 

14 Hardened steel cap for (12) 

15 Key for driving (17) by (12) 

16 Supporting bracket for (17), with bolts 

17 Worm wheel for adjusting device 

18 Worm and worm shaft for adjusting device 

19 Bearing cap for (18) and (11) 

20 Ratchet handle for adjusting device 

21 Drain for step bearing 



237 



bearing is regulated by individual bafflers. Fig. 113 shows the 
type of step baffler used in test. This is the old style of baffler, 
and is not a part of the permanent equipment of the machine. 
The new type will be shown later. The top and middle bear- 
ings are supplied from a manifold, and the flow regulated 



Out/et Qot/onaA 



Baff/er Frame 



Ba/T/er P/ug 



%'f/pe, 




Cap 
Adjust fng Screw 



Wire Gauze 



8/otvOrT 



Stra/ner 



Fig. 113 
STEP BEARING BAFFLER (OLD TYPE) 



by bafflers similar to those used on horizontal machines. These 
bearings are not water cooled. The step bearing (see Fig. 112) 
is piped from the large accumulator line and special care must 
be used in handling this high pressure. It should be remembered 
that the valve stem on the hydraulic valve used in all high pres- 
sure lines is free to turn entirely out of the body of the valve. 
These valves should be opened six turns only. If opened further 
than this the result may be disastrous. 

238 



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239 




SEALING STEAM 



SEC TION A AA -A A -A A 
GZZZZZ* \ 




Fig. 114 

CARBON PACKING (FLOATING RING TYPE) 

1 Carbon packing casing (half) 

2 Clamp bolt for (1) 

3 Carbon ring segment 

4 Retaining bolts for casing 

5 Stop for carbon rings 

6 Bracket for (5) 
6 Garter spring 

8 Alloy packing ring 

9 Retaining ring 

10 Drain to 2nd stage shell 

11 Drain to 3rd stage shell 

12 Drain to atmosphere 

13 Supporting spring 



240 



In turning oil on the step bearing proceed as follows: 

Open the valve until the step is raised and note the gauge 
pressure. Then close the valve, allowing the step blocks to 
come together again. Now open the valve very slowly, and 
watch the gauge. Hold the pressure between 90 and 95 per 
cent of that required to raise the step, and watch for oil leakage 
at the drain from the step. At this pressure the step will not be 
raised, and if the blocks are parallel the leakage between them 
will be practically nothing. However, if the blocks are not 
quite parallel there will be an opening on one side which will 
allow a considerable flow of oil. 

Having ascertained that the step blocks are all right the 
valve should then be opened to give about a quarter of the 
required flow, and the step bearing and pipes allowed to become 
warm. This must be done since the oil will not drain away from 
the step rapidly enough to prevent flooding when cold. The oil 
in the supply tank is kept at a temperature of 45 to 51 deg. cent, 
and a short time should be sufficient to warm up the bearing 
and drains. The valve may then be opened the full six turns. 

A table of the flow and probable pressures for various machine 
capacities is given on page 239. 

This table is calculated for machines that are completely 
assembled. 

It is usually necessary to readjust the baffler between the 
periods of adjusting wheel and field balance. 

Oil leaks in the step bearing should be carefully watched 
for, and remedied before starting the machine. 

Carbon Packing Rings 

The carbon packing rings (see Fig. 114) should have enough 
steam to lubricate, and to seal in case vacuum is used. Too 
much steam is injurious. The right amount will be indicated 
by the escape of a little vapor from the drain leading from the 
carbon ring casing. This drain should always be left open. 
It sometimes happens that, through insufficient steam lubrica- 
tion or other cause, the carbon rings tend to grip the shaft, 
become very noisy and throw the machine into vibration. When 
this occurs, which is more often on horizontal than on vertical 
types, a very thin solution of graphite and water should be 
introduced into the carbon casing. One or two applications will 
effectually remove the trouble. The graphite must never be 
mixed with oil, nor made into a thick solution with water, as 
it then becomes gummy, and causes the rings to stick in the 
casing and hold away from the shaft. When this happens the 
rings cannot seal. 

Trip Rigging 

Before starting a machine, try the trip rigging on the emer- 
gency throttle valve to see that it will trip the valve easily 
See Fig 115. 

241 



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Fig. 115 

THROTTLE VALVE AND EMERGENCY GOVERNOR 
TRIP RIGGING 



1 


Valve bonnet 


11 


Trip bell crank 


2 


Valve body 


12 


Large gland 


3 


By-pass nut 


13 


Small gland 


4 


By-pass valve cover 


14 


Sliding nut 


5 


By-pass valve 


15 


Yoke 


6 


Valve spool 


16 


Trip handle 


7 


Valve stem 


17 


Trip hook 


8 


Valve seat 


18 


Lever for sliding nut 


9 



Trip spring 

Valve stem bushing 


19 


Handwheel 



242 



Wheel Balance 

Before the main valve is opened to admit steam into the 
line to the emergency throttle, the exhaust valve should be 
opened. This will obviate any danger of excessive steam pres- 
sure on the turbine shell should the throttle valve leak. 

Cold machines, in being started, should have enough steam 
given them to start them revolving at once. Otherwise the 
steam may distort the wheels, due to local heating. As soon 
as a machine starts to revolve, place one end of a wrench or 
bar against the intermediate holder, and rest the ear against 
the other end, and listen for rubbing. If the wheels seem to be 
running clear, bring the speed up to about 50 rev. per min., 
and then shut steam off completely. Listen for rubbing as 
before and at the same time notice whether the speed dimin- 
ishes rapidly or not. The time that a machine should run 
before stopping varies greatly with the size and type, hence 
it is left largely to the judgment of the man in charge of the 
machine as to whether it is operating as it should. It is not 
necessary to let the machine come to a stop to see if it is run- 
ning freely, as any marked diminution of speed can be noticed 
in a minute or two. Heat the machine up thoroughly before 
bringing it to normal speed by allowing it to run at about 
one fourth normal speed for fifteen to thirty minutes, depending 
on the size. When well heated, bring to normal speed (if the 
balance permits) and note the balance, or amount of vibration, 
on the bearings and on the intermediate holder. If the balance 
is good enough at normal speed it should then be tried at 110 
per cent normal speed. Balance at 110 per cent speed should be 
as good, or nearly as good as at normal. 

Some machines are in good balance when they come to 
test, but more often they have to be balanced dynamically. 
Before beginning wheel balance, the method of numbering the 
balance weight holes should be understood. It is impracticable 
to mark the wheel alongside the holes themselves, as the steam 
would soon efface the marking, so the following method is used: 

On horizontal machines, holes for introducing balance weights 
into the wheels are provided in the turbine head and in the 
exhaust chamber. The wheels are revolved until a hole in the 
wheel is in line with the hole in the exhaust chamber. This 
is considered hole No. 1. A definite point of reference is made on 
the middle bearing in line with this hole, and a mark made on 
the coupling also in line. This locates hole No. 1 and should be 
permanently indicated by a prick punch mark on the coupling. 
The wheels are now slowly revolved and the location of each 
balance weight hole is marked on the coupling with chalk or 
whiting. Beginning with No. 1 the holes are numbered, always 
in the direction of rotation. 

In vertical machines the holes are numbered in a slightly 
different manner. The coupling is not assembled during wheel 
balance, so a key- way is selected to locate hole No. 1, this 
key-way being indicated by a prick punch mark. The balance 
weight hole in the wheel nearest in line with the key- way is 

243 



brought under the hole in the turbine head and No. 1 marked 
on the bearing under the key-way. Revolve the wheels slowly 
and mark under the key- way on the bearing the location of each 
hole. Numbering on the bearing must be against rotation in 
order that the numbering on the wheels themselves may be in 
the direction of rotation. 

All turbines revolve counter clockwise facing the steam inlet end. 

Before beginning work on balance, the shaft should be painted 
with whiting, at both ends when accessible. When the machine 
is up to speed or at as high a speed as the vibration will permit 
mark the shaft lightly with a pencil. The pencil line will 
appear heavier in one place which is generally opposite or 
nearly opposite the side that requires additional weight. Place 
a weight in the side indicated, in either the first or last stage 
wheel, depending on which showed the greater amount of 
unbalancing as indicated by the pencil mark. Use a fair sized 
weight, e.g., one two inches long. Bring the machine up to as 
high a speed as the balance will permit and note the balance 
of all parts. Then move the weight one-quarter way around the 
wheel and try the balance again. Proceed thus until both first 
and last wheels have been tried. Then continue trials in. the 
holes in which the best balance was noted, using larger or smaller 
weights as may seem necessary. No rigid rule can be set down 
for the size and use of weights in balancing. It is a matter 
which must be left entirely to the judgment of the test man. 
A balance record similar to that given on page 245 should be 
kept, and on this an accurate record of weights used and the 
per cent balance should be noted. 

From this record it is evident that weights in hole No. 7 
gave the best results in "quartering," hence it was then only 
necessary to try slight variations and changes in the neighbor- 
hood of hole No. 7 to obtain a perfect balance. 

A number of things may influence the balance of wheels 
at the start which are not due to an actual unbalancing of the 
wheels themselves. 

(1) The carbon packing rings may be gripping the shaft. 
This has already been discussed, and the proper remedy ex- 
plained. 

(2) The diaphragm packing rings may be rubbing on the 
shaft or wheel hubs. That surface of the packing ring that bears 
against the shaft consists of a series of V-shaped grooves. When 
there are indications of rubbing at this point, the turbine should 
be run continuously at a speed at which there is a slight vibra- 
tion. This will in a short time wear a clearance between the 
rings and shaft and remove the source of trouble. This method 
should be followed in all cases in which a turbine vibrates 
at low speeds, and for which no other cause can be found. 

(3) The wheels may be rubbing at the circumference. When 
this is the case it should be reported at once, and an investi- 
gation made. 

(4) There may be water in the turbine. See that all drains 
are free. If, when opened, neither water nor steam escapes, it 

244 * 





BALANCE HOLE NUMBERS 


PER CENT BALANCE 




1 

n 

2' 


2 
Wl 


3 

light 


4 

2" 

2" 


5 


6 



1" 


7 

2" 



2" 

2" 
2" 

2" 

2" 


8 



2" 
2" 


9 




10 

2" 


11 


12 


v be 


4u 

i— iW 


Is 




I 


93 


95 


54 




I 


90 


94 


55 




I 


92 


95 


93 




I 


97 


97 


95 




I 


93 


95 


94 




I 


93 


94 


93 




I 


95 


97 


96 




I 


92 


95 


92 




I 


98 


99 


98 




I 


99 


100 


98 




I 


100 100 


100 



" O "Indicates the outside, or first stage wheel. 
"I" Indicates the last stage wheel. 

Note — Italics indicate pencil notations by the one doing the 
balancing. 

245 



is evident there is a stoppage somewhere, and all valves and 
piping should be carefully examined. 

CA UTION. Do not run wheels with loose weights. Be sure 
that all weights are tight, and that none project so far on either 
side of the wheel as to strike any stationary parts. 

Field Balance 

The method employed in balancing the field is practically 
identical with that used in balancing the wheels. In this case 
the numbers may be painted directly alongside each balance 
weight screw hole, beginning at the field leads and numbering 
in the direction of rotation. When the field leads are brought out 
on opposite sides of the shaft, hole No. 1 should be indicated by 
a prick punch mark. 

On a later type of field the balance weight screw holes are 
replaced by a dove-tail groove in which are carried the heads of 
the bolts securing the weights. It will be necessary on this type 
to divide the groove into a number of equal sections, or "loca- 
tions" which should be numbered as are the screw holes on the 
older type of field. Twenty-four is the most convenient number 
of "locations" to use. 

On the older type of field the balance should be obtained by 
the use of one weight only in each end of the field. If this is 
impossible and more than one weight is necessary the weights 
must be concentrated, not scattered or counter-balancing each 
other. 

On the later type with the groove, the procedure is some- 
what different. Here the balance weights are always used in 
pairs, i.e., a pair of weights in each end of the field. The weights 
of any one pair must always be equal in size and similar in shape 
and each weight must be secured by at least two bolts. When a 
balance is finally obtained the size of the weights of a pair should 
have been so selected that the weights are located approxi- 
mately 60 deg. to 90 deg. apart. This method of balancing 
allows of a very wide range of adjustment. By bringing the 
weights together or moving them further apart along the groove 
any effective value from zero to a maximum may be obtained, 
and the resultant value may be placed in any position desired. 
If the weights have been selected as directed there will be ample 
latitude for further adjustment should it become necessary at 
any time. 

In all field balance work the shaft should be painted with 
whiting at each end of the field, and indications of the direction 
and amount of unbalancing made as described under the head 
of "Wheel balance." These indications should be used as a 
guide in the location of weights throughout all balance work, but 
the knowledge of how to do this must be gained by experience 
as the significance varies with every machine. 

CAUTIONS 

1. Balance weights must fit tightly, all bolts be inf place and 
drawn up tightly. 

246 



2. Weights must fit firmly for their full length against the 
outer side of the slot. 

3. Xo balance weight should be used whose thickness is 
more than twice the depth of the balance weight slot. 

4. Weights should never be superimposed. 

In loading machines for shutting down, do not load them 
single-phase. 

The foregoing instructions on the balancing of alternator 
fields will also apply, in a general way, to the balancing of direct 
current armatures. The weights used in direct current arma- 
tures are of different shapes, and are secured in various ways, 
but the method employed in obtaining a balance is the same as 
that used in balancing turbine fields and revolving fields. 

Before beginning balance work on any generator, all wiring 
should be completed and cold resistance measurements taken. 

One condition to be watched in all balance work is the number 
of operating valves that are held open. Only just so many 
valves as are necessary to bring the machine up to speed should 
be used. If a greater number of valves is opened a greater 
amount of steam is required to do the same work. This is 
wasteful, and in the case of large machines the steam pressure 
in the mains may be so reduced by the excessive flow as to let 
the step-accumulator down, causing considerable damage if 
not stopped at once. This rule in regard to the number of valves 
opened should, in fact, be observed in the starting of machines 
at all times, especially those of larger sizes. The only case 
in which it cannot apply is in the testing of operating governors 
to be described later. 

Too much importance cannot be attached to the main- 
tenance of steam pressure. Low steam pressure may, through 
the loss of pressure in the step-accumulator oil system as just 
referred to, damage the wheels of a vertical turbine to such 
an extent as to require an entirely new set of wheels. 

Governor Tests 

EMERGENCY GOVERNORS 

After the wheels are balanced and before the field is assembled, 
the emergency governor should be adjusted and tested. There- 
after it should be tripped at least once every twenty-four hours, 
and a record made in a folder provided for this purpose. Emer- 
gency governors are known as Type E. There are two forms 
now used. Form D, the eccentric ring type (Fig. 116) is used on 
all machines of 2000 rev. per min. and under, and Form E, the 
plunger type (Fig. 117) used on the higher speed machines. 

The Form D governor is shown in Fig. 116 in its normal 
concentric position before operating. In operating, the ring 
(1) moves out eccentrically against the spring (13) coming in 
contact with the trip finger (9) (Fig. 118) thereby releasing the 
emergency throttle valve. The adjusting nut (8) (Fig. 116) over 
the spring screws on to the spindle (4). The thread is right- 
handed, so that by turning the nut to the right more tension is 

247 




^^»5-^ 



Fig. 116 

EMERGENCY GOVERNOR (FORM D), (DOUBLE RING 
TYPE, HORIZONTAL TURBINES) 



Emergency governor ring 8 

Emergency governor guide 9 

block 10 

Emergency governor spring 12 

box 13 
Emergency governor spindle 

Emergency governor stop 14 

Bushing for (2) 15 
Collar for (3) 



Adjusting nut for (4) 
Guide pin for (1) 
Cotter pin for (5) 
Bushing for (3) 
Emergency governor 

spring 
Support for (13) . 
Rivet for (1), (2) and (3) 



248 




Fig. 117 

EMERGENCY GOVERNOR,*PLUNGER TYPE (FORM E) 

1 Governor plunger 

2 Tension adjusting bushing 

3 Guide bushing 

4 Retaining nut for spring 

5 Adjusting nut for spring 

6 Governor spring 

7 Cotter pin for retaining nut 

8 Pin for adjusting nut 

9 Clamping collar for governor 

10 Dowel pin for clamping collar 

11 Holes for spanner wrench 

12 Cap screw for clamping ring 



240 




Fig. 1 
EMERGENCY GOVERNOR AND THRUST BEARING 



1 


Pillow block or stand- 


17 


Stationary plate, front 




ard 




thrust 


2 


Gear casing 


18 


Adjusting shims, front 


3 


Shaft 




thrust 


4 


Gauge board 


19 


Bearing cap bolt 


5 


Lock nut for gears 


20 


Bearing cap 


6 


Spiral gear 


21 


Bearing 


7 


Emergency governor 


22 


Babbitt lining 


8 


Deflector 


23 


Bearing packing ring 


9 


Emergency governor trip 


24 


Air deflector 




finger 


25 


Oil guard 


10 


Emergency governor con- 


26 


Adjusting shims, back 




necting rod to throttle 




thrust 




valve 


27 


Revolving plate, back 


11 


Emergency governor rig- 




thrust 




ging bell crank 


28 


Roller cage, back thrust 


12 


Cover plate 


29 


Stationary plate, back 


13 


Emergency trip finger rod 




thrust 


14 


Thrust nut 


30 


Water drain sight cup 


15 


Revolving plate, front 


31 


Bearing standard dowel 




thrust 




pin 


16 


Roller cage, front 


32 


Dowel pin nut 




thrust 


33 


Bearing standard bolt 






250 



given to the spring and the speed at which the governor operates 
is increased. The nut (8) is held in position by a lock-screw, 
which goes through one of the holes in the nut and screws into 
a stationary plate below. This screw must always be replaced 
after it has been removed to make an adjustment of the governor. 

The Form E governor is shown in Fig. 117. Here, instead 
of an eccentric ring, we have a plunger (1) to strike the trip- 
finger. The entire mechanism is contained in a bored out sec- 
tion of the shaft, and held in place by the two clamping rings 
(9,9). The adjusting nut (5) over the spring, does not turn, 
but is moved in or out by turning the bushing (2). Since 
the nut has a right-hand thread, turning the bushing to the 
left, forces the nut in, puts more tension on the spring, and 
increases the speed at which the governor will operate. The 
bushing (2) is held in position and prevented from turning 
by the clamp rings (9), hence these rings must be loosened 
before any effort is made to move the bushing. The rings are 
clamped by four cap screws in the holes (12). 

All emergency governors must be adjusted to trip at 10 per 
cent above the normal speed of the machine, with an allowable 
variation of 3^2 per cent either high or low. The speed at which 
they return to their normal position must be, on the Form D, 
between 90 per cent and 100 per cent of normal speed, and on 
the Form E, between 100 and 101 per cent. After the proper 
adjustment has been obtained, the governor must be tripped 
five or six times in succession, and the operation of all parts 
of the trip rigging noted. There should be no lag to any of the 
parts, and the valve should close quickly. Any defect must be 
reported at once. 

Fig. 118 shows the assembly of a Form D governor and the 
arrangement of the trip rigging. 

This illustration also gives a good idea of the arrangement of 
the thrust bearing and adjusting shims of the roller type of 
thrust. 

Fig. 119 shows the arrangement of a later type of thrust 
bearing known as the "Block" type. This is the type of thrust 
also shown in the illustration of a general turbine assembly, 
Fig. 109. A third arrangement of a thrust bearing, known as 
the "Ring" type is shown in Fig. 120. The Ring type and the 
Block type thrusts are interchangeable. Either may be as- 
sembled in the outer housing (9) Fig. 119. 

OPERATING GOVERNOR 

The operating or main governor is known as Type M gover- 
nor, Form C, and is shown in Fig. 121. 

On vertical machines the governor is set directly on the top 
of the main shaft, see Fig. 108, but on horizontal machines it 
is driven from an auxiliary shaft connected to the main shaft 
by a worm and gear. See Fig. 122 and Fig. 123. This auxiliary 
shaft also drives the gear oil pump. After the gear pump is 
assembled and operative the steam driven oil pump should not 
be used except when starting and stopping the machine. 

251 




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253 




Fig. 120 



RING TYPE THRUST BEARING 

1 Alloy thrust rings 

2 Thrust bearing shell 

3 Thrust bearing 

4 Bolts 

5 Shims for adjusting clearance of wearing shoe 

6 Wearing shoe 

7 Set screw for shaft nut 

8 Shaft nut 



254 



Before beginning governor tests the machine should be run 
for a short time with the governor holding speed to ascertain 
that all parts of the governor and hydraulic rigging function 
properly, that there is no sticking in any part, and that there is 
no hunting in the governor itself. Any defects noted should be 
reported at once and the necessary corrections made before 
proceeding with the governor test. 

OPERATING GOVERNOR TEST 

Fasten a pointer on the machine in some convenient place 
where it will be near the piston or connecting rod (No. 14, 
Fig. 122). Paint the section of rod opposite the pointer with a 
coat of whiting. Move the pilot valve by hand, opening all 
the operating valves. As the last valve opens so that the roller 
12 (Fig. 124) just rises over the point of the cam (14) make a 
mark on the whiting opposite the pointer. Then lower the 
pilot valve stem so that the valves close, and as the last valve 
is just closed make a second mark on the whiting opposite the 
pointer. The foregoing refers to high pressure machines only. 
Machines designed to operate on both high and low pressure 
steam are provided with a low pressure butterfly valve, Fig. 125, 
whose operation precedes that of the high pressure valves. 
Hence the two marks must include the total travel of the piston 
rod (2), necessary to operate both the high pressure valves and 
the butterfly valve. 

The first mark is located as described above. The second 
mark is made when the piston or connecting rod (2), Fig. 125, 
has, by means of the cam (8) and connecting rod (10) brought 
the butterfly valve to the "closed position" as indicated by 
dotted lines. The length of the connecting rod (10) should be 
so adjusted as to give a compression on the spring (5) of from 
s5 to tV in. Having located the two limit marks, divide the 
intervening space into five equal parts, thus obtaining six 
marks. In order to bring the speed above the point at which 
the governor would normally hold the speed, and so make each 
mark on the scale pass the pointer, it is necessary to block open 
one or more valves. Before any valves are blocked open, and 
with the. governor holding speed, check the tachometer.' This 
is done preferably by holding the speeder on the end of the gover- 
nor spindle (8), "Fig. 121, rather than on the end of the main 
shaft. Take a two minute reading. The proper governor speed 
may be determined from the ratio of the worm and gear. The 
tachometer, which is always belted, should be provided with a 
pulley of such diameter as to give a reading well up on the scale. 

All is now ready for the actual governor tests and adjust- 
ments. Speed readings should be taken as the marks on the 
scale pass the pointer, first as the machine is brought above 
normal speed, and again as it falls below normal. 

The first readings are taken with the synchronizing spring 
(27), Fig. 121, set in mid-position; that is/ with the plug (26) 
Fig. 121, set at the mid-position of its travel. All adjustments 

255 




Fig. 121 

OPERATING GOVERNOR 



1 


Governor dome 


21 


Thrust plate for (19) 


2 


Governor lever 


22 


Worm wheel 


3 


Governor bracket 


23 


Worm 


4 


Weights 


24 


Supporting plate for worm 


5 


Fulcrum block for (15) 




wheel 


6 


Links 


25 


Handwheel 


7 


Yoke for (6) 


26 


Plug for synchronizing 


8 


Spindle or connection rod 




spring 


9 


Spring for universal joint 


27 


Synchronizing spring 


10 


Lower spring plug 


28 


Limit switch base 


11 


Main spring 


29 


Limit switch details 


12 


Adjusting nut for (11) 


30 


Trunnion for lever 


13 


Adjusting plate 


31 


Nut for (30) 


14 


Key for (13) 


32 


Stop for weight 


15 


Knife edge for (4) 


33 


Studs for lever bracket 


16 


Transmission roller bear- 


34 


Nuts for (33) 




ing 


35 


Lead screw for (26) 


17 


Lever bracket 


36 


Shaft for worm 


18 


Roller bearing for lever 


37 


Knife edge bearing block 


19 


Bracket for synchronizing 




for (4) and (7) 




gear 


38 


Knife edge for (6) 


20 


Bracket for worm gear 


39 


Upper spring plug 






40 


Stop blocks 



256 





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Fig. 123 

GEAR PUMP AND CASING (OUTSIDE TYPE PUMP) 

(See page 259) 



258 



PARTS OF GEAR PUMP AND CASING (Outside Type Pump) 
(See Fig. 123) 

1 Gear casing 

2 Spiral gear driver 

3 Turbine shaft and keys 

4 Spiral gear driven 

5 Lower bushing (governor end) 

6 Governor and pump shaft 

7 Bronze thrust plate for governor 

8 Steel thrust plate for governor 

9 Upper bushing (governor end) 

10 Keys for (4) and (6) 

11 Steel thrust plate for spiral gear 

12 Upper bushing for (6) pump end 

13 Upper bushing for (14) pump end 

14 Idler shaft for pump gear 

15 Bolt for (1) and (16) 

16 Pump casing 

17 Stuffing gland for pump suction 

18 Stuffing box packing 

19 Pump gear 

20 Plug in bottom of casing 

21 Bottom bushings for (6) and (14) pump end 

22 Pump discharge 

23 Pump suction 



259 
/ 




Fig. 124 

HIGH PRESSURE CONTROLLING VALVE 

1 Adjusting screw for valve spring 

2 Supporting plate for (1) 

3 Spring supporting plate (adjustable) 

4 Controlling valve spring 

5 Stud for spring supporting plate, with nut 

6 Frame for controlling valve, with bolts 

7 Guide plate for valve stem 

8 Upper cup for (7) 

9 Thrust pin 

10 Lower cup for (11) 

1 1 Controlling valve lever 

12 Cam roller for lever 

13 Spindle for cam roller with nut 

14 Cam with key 

15 Cam shaft 

16 Cam shaft bracket with bearing cups and bolts 

17 Gland for packing 

18 Nut for stuffing box 

19 Gnide plate and stuffing box for valve stem 

20 Valve stem 

21 Valve (wing type) 

22 Valve seat 

23 Valve casing 

24 Pin for (20 and (21) 



260 




P OSIT ION OF 
BUTTERFLY VALVE 
WHEN FIRST HIGH 
PRESSURE VALVE 
STARTS TO OPE^ 

FULL OPEN 
POSITION 



Fig. 125 



ARRANGEMENT OF HYDRAULIC GEAR ON MIXED 
PRESSURE TURBINE 

1 Cam shaft for high pressure valves 

2 Piston rod 

3 Pilot valve chest 

4 Hydraulic cylinder 

5 Spring 

6 Cam roller 

7 Slot for cam roller (6) 

8 Cam plate 

9 Cam lever 

10 Connecting rod for butterfly valve 



261 



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Fig. 126 

HYDRAULIC OPERATING CYLINDER AND PILOT VALVE 
(HORIZONTAL TURBINES) 

Pilot valve stem guide 

Pilot valve pivot clamp 

Pilot valve middle bushing 

Pilot valve end bushing 

Pilot valve seat bushing (hardened 

steel) 
Floating lever 
Differential lever 
Link for (18) 
Rod end — adjustable 
Connection to governor lever 



1 


Hydraulic cylinder 


12 


2 


Cylinder head 


13 


3 


Stuffing gland for (2) 


14 


4 


Nut for stuffing box 


15 


5 


Piston 


16 


6 


Piston ring 




7 


Piston rod 


17 


8 


Piston rod nut 


18 


9 


Pilot valve 


19 


10 


Pilot valve chest 


20 


11 


Pilot valve stem 


21 



262 



of the governor must be made with the spring in this position. 
On a properly adjusted governor a set of readings similar to the 
following is obtained. 



Marks 



Accelerating 
Decelerating 
Lag 



1728 

1725 

3 



1740 
1736 

4 



1748 

1743 

5 



1757 

1752 

5 



1770 

1767 

3 



1790 

1786 

4 



Tachometer reading = 1750 
Speed of machine = 1800 

The requirements to be met are as follows: 

(1) Normal speed must be between readings No. 3 and No. 4. 

(2) The total regulation, that is, the difference between 
reading No. 6 accelerating and reading No. 1 decelerating, must 
be between 3.6 and 4.0 per cent of normal speed. 

(3) The "lag" is the difference in the readings accelerating 
and decelerating for the same mark on the rod and must not 
exceed an average of 0.4, or a maximum for any one reading of 
0.5 per cent of normal speed. If the speed or regulation of the 

:rnor is not correct, it can be adjusted by varying the tension 
on the main governor spring (11), Fig. 121, or by changing 
weights in the pockets of the governor weights (4), Fig. 121. 

Increasing the tension on the main spring will raise the speed 
and decrease the regulation. Decreasing the tension lowers the 
speed and increases the regulation. 

Increasing the weight in the pockets of the governor weights 
lowers the speed without appreciably affecting the regulation. 

If the lag is excessive take a set of readings on the governor 
rod (17), Fig. 122, with the rod disconnected from the piiot 
valve. This will indicate whether the excess lag is in the gover- 
nor or in the hydraulic rigging. See Fig. 126. In either case 
the lag should be corrected before proceeding. After the gover- 
nor has been properly adjusted, take three sets of readings 
using the scale or marks laid out on the piston rod, the synchro- 
nizing spring being in mid-position. Then take two sets of 
readings on each of the two limit positions of the synchronizing 
spring: " Spring all in " (maximum compression) and "spring all 
out " (minimum compression). 

Bafflers 

The step bearing baffler, Fig. 127, is furnished with all vertical 
machines, having replaced the old style baffler (Fig. 113), now 
used only as a part of the permanent testing equipment. 

The baffler frame is first tested for sand holes and porous 
places in the casting. It is carefully painted over the entire 
surface with whiting, filled with oil, and kept under a pressure 
of 2500 lb. per sq. in. for 24 hours. If at the end of this time 

263 




Fig. 127 

STEP BEARING BAFFLER (ADJUSTABLE) 

1 Head (inlet end) 

2 Plug for blowoff 

3 Strainer (gauze mesh) 

4 Barrier frame 

5 # Adjusting screw 

6 Head (outlet end) 

7 Washer (inlet end) 

8 Strainer frame 

9 Baffler screw 

10 Washer (outlet end) 



264 



there is no indication of oil anywhere on the whiting, the baffler 
is completely assembled with strainer and plug. 

The plug^ or screw (9), Fig. 127, has a thread with a taper- 
ing depth of groove which allows of a wide range of adjustment. 
The deepest grooves should be assembled at the discharge end. 
The following table shows the approximate flows for given 
pressure drops across the baffler and various adjustments of the 
adjusting screw (5), Fig. 127. The temperature of the oil is 
•50 deg. cent. 

FLOW IN GALLONS PER MINUTE 



\^ Length 
















^^^^ of 
















Drop ^^---^"A" 


2 In. 


3 In. 


4 In. 


5 In. 


6 In. 


7 In. 


8 In. 


lb. per sq-t n. ^^~~^~ 
















50 


1.0 


2.2 


3.1 


4.4 


6.0 


8.0 


12.5 


75 


1.5 


2.9 


4.2 


5.4 


7.6 


10.7 


16.8 


100 


1.9 


3.4 


5.0 


6.5 


9.0 


12.7 


20.5 


125 


2.2 


3.9 


5.5 


7.4 


10.1 


14.5 


24.0 


150 


2.4 


4.4 


6.3 


8.4 


11.2 


15.6 


27.5 



"A" is the distance between the end of the plug and the 
baffler head. See Fig. 127. 

Stage Valves 

In most of our multi-stage vertical turbines, valves are pro- 
vided which open additional second stage nozzles at times of 
overload. 

The usual arrangement of this valve is shown in Fig. 128. 
The pipe (16) connects with the first overload valve on the 
operating valve casing. When the operating valve is opened 
steam is admitted to the upper side of the piston (14) and the 
stage valve (2) is forced open against the spring (5). This 
valve should open quickly and positively, and should close in 
the same way. 

The only test made on the assembled stage valve is to open 
and close the controlling valve a few times, and note that the 
stage valve acts properly and operates without sticking. Also 
the travel of the stem or indicator rod (8) should be measured. 

A modification of this valve carries the spring outside of the 
casing, but the operation is essentially the same. 

GENERATORS 

Sectional views of vertical and horizontal turbo-generators 
ai^ shown in Figs. 129 and 130. 

The scheme of ventilation of the turbine generator is rad- 
ically different from that of other types of generators. Referring 
to Fig. 129, air is drawn in through an opening in the side of 
the hood (9), forced by the fans (21), through the air gap and 
out through the ducts in the armature laminations (1) to the 

265 




Fig. 128 
STAGE VALVE (See page 267) 



266 



PARTS OF STAGE VALVE. (See Fig. 128) 

1 Casing for stage valve 

2 Valve and piston 

3 Valve seat 

4 Cylinder lining 

5 Spring 

6 Cylinder head 

7 Adjusting screw 

8 Indicator rod 

9 Balance-cylinder head and stuffing-box 

10 Gland for stuffing-box 

11 Spring seat 

12 1 

12 r Rings for piston 

13 Indicator 

14 Balance piston 

15 Packing ring for balance piston 

16 Admission from overload operating valve 

17 Drain for valve 



2G7 




Fig. 129 

VERTICAL GENERATOR SECTION 



1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 



Armature punching section 16 

Armature punching space block (outside) 17 
Armature punching space block (inside) 18 

Armature spider 19 

Armature flange (top or lower) 20 

Armature key 21 

Armature coil 22 

Bearing bracket (upper) 23 

Ventilating hood 24 

Floor plates 25 
Generator base and middle bearing bracket 26 

Pole piece revolving 27 

Revolving field spider 28 

Field spider rings 29 

Shaft 30 



Field coil support 

End flange 

Field coil retaining bolts 

Retaining rings 

Field coil 

Fan 

Air deflector (upper) 

Air deflector (lower) 

Collector lead supports 

Brush-holder studs 

Collector 

Field lead 

Brush-holder lead 

Binding bands 

Coupling 



268 



space between the laminations and the armature shell (4) and 
thence downward to be discharged through openings in the gen- 
erator base (11). 

The ventilation scheme on the horizontal generator, Fig. 130, 
is similar to that on the vertical, except that air is drawn in 
from below at both ends. The air is forced by the fans through 
the air gap and out through the laminations, and may be dis- 
charged at either the top or bottom of the armature as the 
customer may require. 

On small machines of 1000 kw. and less, the fans are usually 
omitted from the field. On machines in test, where a bottom 
discharge is called for, the opening at the bottom of the armature 
is temporarily blocked off, and the air taken from the top. 
Otherwise, a more or less elaborate arrangement of air ducts 
would be necessary to prevent the hot discharged air from being 
drawn in and circulated through the armature over and over 
again. 

Generator Tests 

ALTERNATORS 

Generator tests comprise the lesser part of the work on tur- 
bine sets. On standard machines, and those for stock, the only 
tests usually required are saturation and synchronous impedance 
curves, phase rotation, current leakage from shaft to pillow 
block, field and armature measurements, and high potential 
tests. These tests are invariably made on every machine. 

In addition to the above, heat runs, either open circuit and 
short circuit, or a "zero power-factor" run may occasionally 
be called for. Other tests much less frequently made are ven- 
tilation tests, motor core loss, phase characteristic, armature 
impedance with rotor removed, open-delta heat runs, zero- 
excitation heat runs and full load heat runs. 

As all the above mentioned tests except ventilation tests 
and "zero-excitation runs" have been dealt with elsewhere 
in this book no further mention is necessary except such details 
as may need special attention due to slightly different condi- 
tions that may be found on turbine generators. 

Before beginning generator tests all pipe joints, and joints 
about the gear casing, pump and bearings where there is a 
possibility of oil leakage, should be carefully painted with 
whiting so that any leaks existing may be located during the 
progress of generator tests. 

The limits to which saturation and synchronous impedance 
curves are to be run, and the values of voltage and current held 
on open- and short-circuit heat runs are varied from time to 
time under instructions from the turbine generator Engineers, 
hence, the book of "Special Instructions" previously referred to 
should be consulted for this data. 

Cold Measurements 

Under the head of "field balance" reference was made to 
taking cold measurements on the generator. This should be 

269 




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271 



done invariably before the field has been run. In addition to 
galvanometer measurements of the armature and field, the field 
is also measured by the voltmeter-ammeter method, as a basis 
for the field temperature measurements to be made and recorded 
with each half-hourly reading during the heat runs. When an 
armature is equipped with temperature coils these must be 
measured at the same time the other measurements are taken, 
both before and during heat runs. The information obtained 
from temperature coil measurements is the most important of 
any obtained from heat runs on a turbine generator, for it is by 
this means only that the actual internal temperatures of the 
armature can be learned. Hence, it is of the utmost importance 
that an absolutely accurate record of the cold resistance and 
temperature of these coils be made. 

Shutting Down After Heat Runs 

Whenever possible an alternator should be so wired that it 
may be quickly shut down after a heat run by loading it on 
water-boxes. The load must be three- or quarter-phase, as 
the case may be, never single-phase, and should be reducedas 
the machine slows down in order not to increase the heating 
due to decrease in ventilation. 

In some instances it is impracticable to load on water-boxes, 
and when such is the case the Head of the test, or an assistant, 
should be consulted as to the best method to be used in shutting 
down. 

Direct current machines should always be arranged for 
separate excitation for shutting down rapidly, and always 
provided with a water-box load, even when the tests and heat 
runs are being made by the "feeding-back" method. 

Running Turbine Sets as Motors 

When a turbine set is "motored" for a zero power-factor 
heat run, or any other test, special attention should be given 
to heating in the turbine. The friction of the air on the buckets 
will raise the temperature of the wheels to a degree far above the 
temperature of steam, and will cause serious trouble. To 
obviate this, the exhaust should be left open and a slight amount 
of steam passed through the turbine. This will hold the tem- 
perature down to a safe value. It is also necessary to keep steam 
turned on the carbon packing rings to prevent their cutting 
and scoring the shaft. 

"Zero Excitation" Heat Run 

A certain amount of heating on a turbine-generator is caused 
by the friction of the air which is forced through it at a high 
velocity. To determine this heating a heat run is occasionally 
made with no excitation on the field. Two hours are usually 
required to bring temperatures constant, the field being measured 
at intervals in the'usual manner, but with a very small current 

272 



in order to prevent heating from this cause. The current should 
be on only long enough for a quick reading. At the end of this 
run the armature and field should both be measured and final 
temperatures by thermometers taken as on any other heat run. 

Ventilation Tests 

When ventilation tests are to be made, a special pipe for 
this purpose is erected on top of the armature. There are 
two sizes of pipes in use at the present time, one, of 30 in. 
diameter for use on smaller machines, and another of 40 in. 
diameter for the large machines, both rising about 12 feet above 
the generator. Reducing cones may be fitted to the upper end 
for varying the diameter of the outlet, and a butterfly valve 
is sometimes inserted between the lower end of the pipe and 
the armature opening, for varying the volume of air from a 
maximum to zero. The manometer used in measuring volume 
is connected either to an impact tube located in the center of the 
plane of the outlet opening, or to a special plug inserted radially 
in the air pipe near the top, but below the base of the cone. 

On machines of 1000 kw. and less, readings are taken with 
the impact tube only. Above 1000 kw. both methods are used. 
Simultaneously with every manometer reading, readings of 
the pressure inside the inner shields of the armature (see Fig. 
130) are taken at each end of the armature, a U-tube being used 
for this purpose. The pressure in the shields is also taken 
occasionally with the opening in the armature entirely closed, 
that is, with no air circulating through the generator. 

Testing Record Sheets 

There are certain items and questions on turbine generator 
sheets which do not appear on sheets for other forms of gen- 
erators, hence, these sheets should be carefully looked over 
and these items noted. It is important that they be checked 
carefully and that questions be answered in every case. 

DIRECT CURRENT MACHINES 

The only tests made on direct current machines are saturation, 
shunt adjustments and heat runs. 

Compound is always adjusted for a rise in speed of 2 per cent 
from full load to no load. As steam conditions in the Testing 
Department are not the same as those under which a machine is 
to operate when permanently installed, the governor cannot be 
relied on to give the proper 2 per cent regulation, hence, it is 
necessary to vary the speed as required by means of weights on 
the governor arm. 

DEFECTS 

After tests are completed, the entire machine, both turbine 
and generator, should receive a thorough inspection for any 
defects which may not have been previously corrected during 
the tests. 

273 



All defects, large and small, should be carefully noted and 
recorded on regular "defect sheets," special attention being 
given to steam leaks and oil leaks, and oil throwing at bearings, 
If any doubt exists as to whether or not some particular condi- 
tion is to be regarded as a defect, enter the item on the sheet 
as though it were a defect, and if on investigation it is found 
not to be, it can easily be marked off. 



STEAM CONSUMPTION TESTS 

These tests are conducted in order to check guarantees 
made to customers or to obtain engineering information on new 
or experimental machines. 

In either case it is essential that accurate and thoroughly 
reliable data be obtained, and to this end every man concerned 
with the test must be held responsible for his individual part of 
the work. 

Assembly of Machines 

While the machine is being assembled the following record 
should be made: 

The number of the Drawing List. 

What combination is assembled in the turbine. 

Changes made since previous test. 

Any special features of construction. 

During the assembly of the turbine, all necessary drilling 
and piping for gauges and thermometer wells should be done 
and a calibrated orifice should be placed in the feed pipes to 
the carbon packing rings in order that the amount of steam 
necessary to seal the rings can be determined. Before the steam 
piping is assembled a very accurate measurement of the pipe 
diameter should be taken at the point where the nozzle plug for 
the steam flow meter is to be installed. 

If a water-brake is to be used for load, it is absolutely neces- 
sary that the brake hang free on the knife edges for a very 
little friction will give very erratic results in the scale reading. 

Preparation for Test 

The electric meters to be used in the test should be newly 
calibrated. Where exceptionally accurate results are desired, 
it is well to calibrate the meter transformers although as a 
general rule their calibration changes very little. In case a 
water-brake is used, the scale should be adjusted, using the 
standard weights furnished for that purpose. 

It is sometimes very difficult to obtain the required amount 
of vacuum when the turbine is first started. Therefore, after 
the turbine is assembled and before starting the test, the ma- 
chine should be run under load to determine if the required 
vacuum can be obtained. In case this is impossible, it is neces- 
sary to find the air leaks and stop them up. Large leaks can be 

274 



found by holding a lighted torch near the crack, the air current 
drawing the flame in with it. Leaks can sometimes be found by 
applying soapsuds to the leaky joint. Leaks that cannot be 
closed by tightening the bolts should be subjected to a few inches 
of vacuum and the leading joints then painted with thick black 
japan. A serious leak may be closed by caulking with lead or 
solder and afterward painting with japan. 

Readings Taken During Test 

The following readings should be taken during test: 

Pressures (or vacuum), 

Temperatures, 

Flow, 

Load. 

Pressure 

The pressures to be read are: 

Steam pipe (above throttle and strainer), 

1st valve bowl, 

Operating valve bowl, 

Shell pressures of all stages (when called for), 

Exhaust chamber (near exhaust opening), 

Carbon packing steam. 

The steam pressure is read outside of the emergency throttle 
valve and strainer, and is held constant during the test by 
throttling down the steam, at boiler pressure, with a specially 
equipped valve. The man holding this pressure should at once 
notify the man in charge of the test if the pressure cannot be 
held constant. 

The bowl pressure is taken on the steam passage between 
each of the controlling valves and the 1st stage nozzle. The 
bowls are numbered in the order of their opening, the first 
one to open being No. 1. The pressure on this bowl is read as 
well as the pressure on the bowl on which the governor throttles, 
both readings being recorded every two minutes. Knowing 
the area of the nozzles open, the theoretical steam flow can be 
calculated and used to check the flow recorded. 

Stage shell pressures are read on each stage just below the 
wheel and above the diaphragm for the next stage. The first 
stage should be equipped with both a siphon and a quill, to 
read either pressure or vacuum. If there are more than four 
stages the second stage may need a similar equipment but 
the lower stages only need a quill. The 1st stage pressure is 
read at two minute and the lower stages at four or six minute 
intervals. 

The quill for the exhaust pressure should be tapped into the 
connection between the turbine and condenser close to the 
exhaust opening of the turbine. 

Gauges are used to read all pressures above atmosphere, 
and they should always be calibrated with a dead weight tester, 
both before and after test. Before shutting down, except in 

27.5 



case of an emergency, all gauges should be shut off to prevent 
being subjected to a vacuum. If this occurs, the needle may 
be drawn back against the stop pin so forcibly as to alter the 
calibration. The calibration may also be changed by sudden 
jars or by heating. To prevent the latter, all gauge piping 
must be equipped with a siphon, which is kept cool by applying 
wet waste. If a gauge is allowed to heat up, the solder in the 
Bourdon spring will melt and ruin the gauge. 



+W.C." 




1 

1 

<0 



*£>» 










Fig. 131 
WATER COLUMNS ON GAUGES 



The water column on the gauges should be measured and 
entered on the testing Record Sheet with the number of the 
gauge. The water column is measured from the top of the 
siphon coil to the center of the gauge and recorded as + or — WC 
in inches. (See Fig. 131.) 

U-tubes are used to read all vacuum and pressures of a 
few inches. These consist of a thick glass tube with }/% in. 
bore bent in the shape of a U, and mounted in a wooden case 
carrying a brass scale. (See Fig. 132.) The scale is graduated 
in inches with a zero at the center and numbered each way 
to read at least 16 in. The tube is then rilled with mercury. 
The U-tube is connected up through a heavy rubber tube. 
The glass tube should be clean and free from water and the 
connections should be free from air leaks. These may be detected 
by turning the cock off, leading to the vacuum being measured, 
and noting if any perceptible fall of the column occurs. Both 
columns should be read and added together. Never read one 

276 



and multiply by two. When the U-tube is disconnected both 
columns should stand at the same level. When reading vacuum 
the U-tube may be left connected to the machine, but it should 
be disconnected after each pressure reading, or the tube will 
gradually fill with water. 





Fig. 133 
ABSOLUTE PRESSURE GAUGE 



Absolute pressure gauges are used only on the high vacuum 
of the exhaust, to check the U-tube. These are made of a thin 
glass tube bent in the shape, of a U with one end longer than 
the other. The longer end is bent over and brought down 
below the bottom of the U. (See Fig. 133.) The short leg of 
the U and a couple of inches of the other leg is completely 
filled with mercury, which is then boiled out and the top sealed. 
The whole tube is then mounted in a wooden case carrying a 
brass scale graduated in inches. The lower end is connected 
to the vacuum to be measured by a heavy rubber tube. 
Normally the difference in the heights of the two columns 
will be six to eight inches, but with a high vacuum on the lower 
end they will tend to equalize. The upper column has an 
absolute vacuum on it so that the difference in the height of 
the two columns represents the difference between the vacuum 

277 



being read and an absolute vacuum, or the absolute back pres- 
sure. The sum of the readings on the absolute gauge and the 
U-tube should check the barometer reading within less than 
0.1 in. 

The mercury in the end ,open to the atmosphere slowly 
oxidizes and when this takes place the absolute gauge will 
record a smaller back pressure than is actually present. The 
gauge should be placed above the opening into the vacuum 
space and the rubber tube kept free from loops or water may 
lodge in it and be carried over on the top of the mercury when 
the vacuum is broken. If this occurs, the gauge must be sent 
to the laboratory and cleaned and refilled. The gauge must 
always be kept in a vertical position and never laid down or 
carried horizontally, or air will get into the sealed end. Turn 
on to vacuum very slowly and never take it off suddenly, or 
the mercury may break the sealed end. 

Temperatures 

The temperatures to be read are: 

Steam pipe (near pressure gauge), 

All stage shells (when called for), 

Air (near U-tubes and absolute gauges). 
The temperature of the initial steam is read as nearly as 
possible to the pressure gauge, the thermometer-well being 
placed diametrically in the steam pipe. Steam is available at 
any pressure up to 200 lb. gauge, and of varying quality. For 
running tests, which require high pressure arid low superheat, 
it is sometimes necessary to inject a spray of water into the 
steam. This is done at a considerable distance from the turbine 
in order to get a good mixture of water and steam. When dry 
steam is specified, it is best to hold about 15 deg. superheat; 
for, if a lower superheat be held, the temperature may drop to 
the saturation point where the condition of the steam cannot be 
determined without a calorimeter. " " ' 

When the testis finished, always shut off injection water to 
avoid filling the steam pipe with water, as this would cause a 
water hammer when steam is again turned on. 

In cases where it is necessary to read the temperature in 
the various stages, the thermometer wells should be located 
near the gauge and in the path of the steam; special precautions 
being taken so that the revolving part of the turbine will not 
strike the thermometer well. 

The temperature of the air near all U-tubes and absolute 
gauges is taken in order to correct the length of the mercury 
column to the same temperature as that at which the barometer 
reading is read. 

The man reading temperatures should fill the thermometer 
wells with mercury and be sure that there are no broken mercury 
columns in the thermometers in use. A thermometer should be 
placed as low in the well as possible with the readings to be 
taken, but do not have the mercury column below the point of 
immersion as vaporization of the mercury in the thermometer 
may take place. 

278 



Flow 

There are two methods in common use of measuring the 
quantity of steam to be consumed: The first is to weigh the water 
after the steam has been condensed in a surface condenser. The 
second is to measure the steam flow by means of a steam flow 
meter. 

The first method is the one most commonly used in the 
Testing Department, although in nearly all cases a flow meter is 
installed and readings recorded. 

Flow Tanks 

After the steam has been condensed in the surface condenser 
it is pumped from the hot well to the flow tanks where it is 
weighed. These tanks should be of sufficient capacity to hold 
the amount of steam condensed during six minutes. They are 
mounted one above the other. Both outlet pipes should be 
equipped with quick closing valves which shut perfectly tight. 
The upper tank is used as a reservoir, when taking weights 
on the lower, which is mounted on a pair of platform scales. 

To measure the amount of condensed steam, proceed as 
follows: Close the upper tank outlet valve on an even six 
minutes. Then close the lower tank outlet and balance the 
scale. This reading is called "tare." The upper valve is then 
opened, and closed after exactly six minutes have elapsed from 
the first closing. After closing, the scale is again balanced, 
and this reading is called "gross." The difference between the 
"gross" and "tare" is the "net" reading which when multiplied 
by 10 gives the flow per hour. After taking the "gross" reading, 
the lower valve is opened and the water allowed to run to waste. 
The valve is then closed and the "tare" again taken. This 
cycle is repeated as long as the test continues, care being taken 
to close the upper valve at exactly each six minute interval. 
If the flow is extremely rapid, readings may be taken at four 
or even three minute intervals. Slight variations will occur 
due to irregular pump or condenser action, but the average 
of a number of readings will give accurate results with constant 
conditions. At least five readings should be obtained for each 
load, or operating condition. 

Before taking any readings, the scales should be carefully 
inspected to see that the platform and the scale beam move 
freely. The scales should be calibrated frequently. This can 
be done by balancing the scales and then adding a 50 lb. standard 
weight. These should be placed on each of the four corners of 
the platform. The scales should be thoroughly overhauled 
occasionally and all knife edges kept sharp. When not in use 
the weight should be taken off the knife edges, by throwing 
the lever to the off position. 

Load 

There are two methods of obtaining load; one with an electric 
generator, and the other by the use of a water brake. 

279 



When an electric generator is used, the load is measured 
by means of wattmeters; ammeter and voltmeter readings 
being taken as a check. 



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Ammeterj 



Wattmeters 



Vto/tmeterj 



Fig. 134 
WIRING CONNECTIONS FOR LOAD TEST 



The meters required for reading the load on three-phase 
a-c. generators are: Two wattmeters, three a-c. ammeters, 
two a-c. voltmeters, one d-c. ammeter, and one d-c. voltmeter. 
Each a-c. instrument is provided with a separate potential or 
current transformer of sufficient ratio to bring the reading well 
within the scale of the meter. Five current and four potential 
transformers are required. (See Fig. 134.) 

One side of the current transformer secondary is grounded 
and each circuit is provided with a single-throw, single-pole, 
short-circuiting switch, which must be used when the meter 
is disconnected. The volts, amperes and watts are read, using 
a separate transformer, to check the correctness of the load and 
the power-factor, which should be greater than 0.99; otherwise, 
the test cannot be accepted. The meters and transformers should 
be calibrated frequently, and a copy of the calibrations kept at 
hand for calibrating the load. A record of the number and date 
of calibration of each meter and the number, ratio, and date of 
calibration of each transformer should be entered on each sheet 
of every test. 

The man reading the wattmeters is responsible for the 
load, and, assisted by the man reading the ammeters, must keep 
the phases as nearly balanced as possible. Average readings 
are taken at two-minute intervals; all readings being taken as 
nearly simultaneously as conditions permit. The man reading 
the voltmeters must hold the voltage constant by varying the 

280 



field, when the governor is operating, and must read and record 
volts field and amperes field at four-minute intervals. 

Quarter-phase generators require one less current trans- 
former and one less a-c. ammeter. On d-c. generators, two 
sets of milli-voltmeters with shunts and two voltmeters are used 
to check the load. Considerable trouble is often experienced 
in getting shunts that will check within 1 per cent after they 
have been heated. 

In cases where a water-brake is used, the same precautions 
concerning the care of the scales for the steam flow tanks apply- 
to the water-brake scales. The knife-edges on the brake shell 
should bear properly and the brake shell turn without friction. 
Readings should be taken only when the scales remain balanced 
for an appreciable length of time and when the speed is exactly 
right. Care should be exercised to make sure that water is 
continually flowing through the brake in order to prevent exces- 
sive heating. The flow of water on each side of the brake disk 
should be very nearly equal; otherwise, the brake may vibrate 
severely, making it impossible to obtain accurate readings. 

The following formula is used to calculate the kw. output: 

Let R = Length of brake arm in inches. 
P = The load on scales in pounds. 
5 = Speed in revolutions per minute. 

Then h.p. output = 12X33QQ0 

Kw. output = h.p. output X 746 

Tests 

The tests generally required are "load curve" and "no load 
flow with field excited" and vacuum and speed curves at various 
loads. The following may also be required: Bowl pressure 
curve, superheat curve, and shell pressure curve. 

The readings to be taken and the time intervals are as 
follows for all tests: 

Pipe pressure 2 minutes 

Valve casing 2 

1st bowl 2 

Throttling bowl 2 

Superheat 2 " 

1st stage shell 2 or 4 minutes 

2nd " " 4 or 6 

3rd " " 4 or 6 

Additional shells 4 or 6 

Exhaust-vac. and abs 2 minutes 

Packing steam exhaust and head if used. . .6 to 10 minutes 

Temperature of all U-tubes 10 minutes 

Flow (water rate) 6 

A-c. watts 

A-c. amperes \ 2 

A-c. volts J 

Field amperes and volts 4 

D-c. amperes 1 9 << 

D-c. volts / z 

281 



In taking a load curve (water rate with load) with the gover- 
nor operating, the initial pressure, superheat and vacuum are 
held constant, and at least three, and preferably five, loads are 
used. These may be half-load, full-load, and 50 per cent over- 
load, together with the quarter-load and 25 per cent overload. 

"No-load flow" is taken by running the machine under 
normal steam conditions; holding normal voltage on the generator. 

A vacuum curve may be run with or without the governor. 
When the governor operates, the initial pressure, superheat 
and load are held constant and the vacuum varied. For a 
short vacuum curve four or five points are taken at pressures 
varying 1 in. If it is desired to carry the test to atmospheric 
pressure, two or three of the higher vacuum readings are taken 
close together and the pressure differences then gradually 
increased to five or six inches at atmosphere. The same read- 
ings are taken as on the load curve. 

In running a vacuum curve without the governor, a number 
of valves are blocked open to give approximately the desired 
load at 28 in. vacuum. The speed is held constant by varying 
the load and readings taken on the table, only when the speed, 
initial pressure, superheat and vacuum are correct. They are 
then taken at 1 minute intervals. All other readings are the 
same. The field amperes are held at the constant value, which 
gives normal voltage at normal speed. The water flow will 
be constant at the different vacuums so that the vacuum can be 
changed as soon as a sufficient number of steady readings 
on the table are obtained. Usually not more than four points 
are taken, at 1 in. pressure differences. 

This test and the speed curve are the two most difficult 
water rate tests to make. Every man must work together, 
or the speed will continually vary and no results be obtained. 
The load should be varied in small increments and sufficient 
time allowed for a corresponding change in speed. The field 
amperes should be held absolutely constant as but a small 
change in excitation produces a large change in the load, espe- 
cially on high voltage machines. 

On a speed curve, the conditions are similar to that in a 
vacuum curve without governor and the same precautions 
apply. The speed is varied by varying the load, and field 
amperes are held constant to give normal voltage at normal 
speed. If, however, at the higher speeds the voltage is too 
high either for the safety of the windings or for the meters, 
the excitation may be reduced sufficiently to enable readings 
to be taken. 

Maximum load non-condensing may be taken from a point 
on the normal load vacuum curve by a separate test. Occasion- 
ally back pressure curves above atmosphere are required. 

If the turbine has no atmospheric exhaust openings the 
back pressure test can be obtained only by throttling down 
the air pump until atmospheric pressure is obtained at the 
exhaust opening of the turbine. This produces a high temper- 
ature in the condenser and is likely to cause leaks. 

282 



If, as is usual, the machine has atmospheric exhaust openings, 
they can be piped to the condenser through a gate valve, the 
condenser exhaust being blanked off. With this arrangement 
any desired back pressure may be held on the turbine, while 
the condenser is working under a high vacuum. The condenser 
is kept cool and there is no danger of damaging it or the air 
pump. The readings are the same as for the load curve. The 
load should be gradually increased until the last valve is practi- 
cally wide open. If too much load is applied, the speed will 
fall off when the last valve is wide open. 

A bowl pressure curve is generally taken at full load, with 
the governor operating. The range of initial pressures should 
be as large as possible, in order to neutralize the effect of throt- 
tling on any of the valves. All readings are taken in the same 
manner as for a load curve. 

.4 superheat curve is generally taken at two points, though 
more may be taken, one at low and the other at high superheat. 
The conditions and readings are the same as for the load curve, 
with which it may often be combined to advantage. 

A shell pressure curve is taken on those turbines that are 
equipped with stage valves, or with a movable diaphragm 
between stages. 

This can generally be combined with the load curve. The 
group of nozzles controlled by the stage valve should always 
be wide open or closed tightly. They should never be throttled, 
as this will invariably increase the water rate. 

Arrangement of Apparatus 

In order to conduct the tests outlined on the previous pages, 
the Testing Section in Building Xo. 61 is equipped with appara- 
tus especially arranged for this work. 

Steam Controlling Equipment 

There are four stands equipped with connections to the 
condensers and with a suitable switchboard for controlling 
the generator load. The condensers and their auxiliary appa- 
ratus are located under the switchboards in such a manner that 
they are readily accessible for repairs. The cooling water pump 
is located at the end of the Test Floor, the piping being so 
arranged that it can supply cooling water to one or both con- 
densers at the same time. There are two hot-well pumps and 
the piping is so arranged that either or both pumps can be con- 
nected to either of the condensers. Each pump has a separate 
discharge line to the weigh-tanks. The air pumps are located 
as close to the condensers as possible. 

The condensers are equipped with relief valves set to operate 
at slightly above atmospheric pressure. These valves should 
be inspected frequently to make sure that they are in operating 
condition, for it is a very dangerous practice to allow the pres- 
sure on the condensers to become excessive. 

283 



Electrical Equipment 

Each of the four stands have switchboards so arranged 
that any of the stands can be connected to the water-boxes and 
to the exciters through a plug board. The switchboards are so 
connected that the instruments and transformers can be installed 
without any changes in the permanent winding: The exciters, 
two in number, are turbine driven sets, the fields of both being 
excited from the 125 volt shop circuit. Located directly back 
of the Testing Section office are the water-boxes used for obtain- 
ing load. The blades are remotely controlled, the controls being 
wired to the plug-boards so that they can be connected to any 
of the four stand switchboards. 

Auxiliary Pumps 

Injection water pumps for controlling the superheat, the step- 
bearing oil pumps, oil tanks, and other auxiliary apparatus are 
also located near the testing stands. When running a vertical 
machine it is well to detail a man to watch the step-bearing 
pump as there is no accumulator in the oiling system. 

Caution 

Although there is a regular attendant, whose duty it is 
to operate the pumps, exciters, etc., the man running a machine 
should know at all times what apparatus is in use and should be 
certain that the water, vacuum, and oil pumps are running 
before starting the turbine. When a turbine has been shut 
down for any length of time, the attendant should be notified 
so that he can shut down the auxiliary apparatus or make other 
changes that are necessary. In general all instructions applying 
to commercial testing of turbines apply and should be adhered to 
when taking steam consumption tests. 



284 



CHAPTER 14 

MARINE ENGINE SETS 

The Marine Engine Sets consist of vertical type double 
acting steam engines direct connected to multipolar generators. 
(See Fig. 136.) 




Fig. 135 
MARINE ENGINE 

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287 



ENGINE 

Single cylinder engines are used with generators from 2% 
to 60 kw. capacity, and vertical tandem compound engines with 
machines from 25 to 75 kw. capacity. The engines are standard 
commercial machines. See Fig. 135. 

Steam Pressures 

The ratings of the standard single cylinder engines are based 
on the steam pressures given in the following table and those 
designed for 80 lb. steam pressure can be operated at pressures 
up to 125 lb. either condensing or non-condensing. If higher 
boiler pressures are used a suitable reducing valve must be 
placed in the steam line to give the desired pressure. For steam 
pressures of less than 80 lb., single cylinder engines are fitted 
with large cylinders, to operate at pressures ranging from 35 to 
60 lb. The tandem compound engines are designed to operate 
economically at 125 lb. condensing or 140 lb. non-condensing. 

Unless otherwise advised by Engineering instructions, all 
engines must be tested at the pressures given in the tables on 
pages 289 to 292 inclusive. These tables are a complete list of 
all types of engines manufactured. 

Lubrication 

Two systems of lubrication are used, gravity and forced. 

In the gravity system all the main bearings of the engine are 
lubricated from an oil reservoir attached to the engine (refer to 
Fig. 136) ; each bearing being provided with an adjustable sight 
feed for regulating the flow of oil. The waste oil collects in a 
bedplate reservoir, from which it can be drained, filtered and 
used over again. The bearings of the governor and valve gear 
are lubricated by compression grease cups. 

In the forced system the lubricant is passed under pressure 
to the various parts of the engines. The base of the engine forms 
an oil tank to which is attached a small plunger pump driven by 
an eccentric on the shaft. The oil is forced through grooves in 
the main bearings, drilled holes in the shaft connecting these 
grooves with the crank pin. The oil is also forced to the wrist 
pin through the pipe on the side of the connecting rod. 

The passages in the crosshead pass the oil from the wrist pin 
to the guides. After passing through the bearings the oil is 
collected in the base, where it settles and is used over again. 
The bearing caps must be set up tight and the main bearing 
liners must be close to the shaft; otherwise too much oil leakage 
will occur before reaching the last bearing. To prevent the 
entrance of foreign matter a strainer is attached to the suction 
valve of the pump. When the crank chamber is inspected, no 
waste, dirt or other matter must be allowed to enter and mix with 
the oil. When cleaning the oil chamber, canvas and not waste 
should be used, since the latter clogs the strainer. 

Only mineral oil should be used for lubricating. Since the 
oil passes through the bearings repeatedly, it gradually loses its 
lubricating properties, becoming thick and gritty. It should, 

288 



SINGLE VERTICAL CYLINDER ENGINE SETS, 
GRAVITY LUBRICATION TYPE 





DIMENSIONS IN INCHES 










Dia. 




Dia. 


Dia. 
Ex- 
haust 
Pipe 


Volts 
Full 


Amp. 
Full 


Steam 
Pres- 


Classification 


Cyl- 
inder 


Stroke 


Steam 
Pipe 


Load 


Load 


Lb. 


MP 4- 2 3^-700 


3 Mi 


3 


% 


1 


110 


23 


80 


MP 4- 3 -700 


3K 


3 


% 


1 


110 


27 


100 


MP 4- 4 -600 


4^ 


4 


1 


IV 


110 


36 


80 


MP 4- 5 -600 


4K 


4 


1 


Wa 


110 


45 


100 


MP 4- 7 -550 


5 


4H 


Wa 


m, 


110 


64 


80 


MP 4- 8^-550 


5 


4^ 


Wa 


IV?, 


110 


77 


100 


MP 6-10 -450 


QV?, 


5 


IV?, 


2 


110 


91 


80 


MP 6-12^-450 


W, 


5 


IV?, 


2 


110 


114 


100 


MP 6-15 -400 


8 


6 


2 


2V? 


110 


136 


80 


MP 6-17K-400 


8 


6 


2 


2V?, 


110 


160 


100 


MP 6-20 -360 


9 


7 


2 V?, 


3 


125 


160 


80 


MP 6-25 -360 


9 


7 


2 V? 


3 


125 


200 


100 


MP 6-30 -305 


11 


8 


3 


m 


125 


240 


80 


MP 6-35 -305 


11 


8 


3 


3V?, 


125 


280 


100 


MP 6-40 -305 


11 


8 


3 


SV2 


125 


320 


125 



Generators can be wound for 110, 125 or 250 volts. 



SINGLE VERTICAL CYLINDER ENGINE SETS, 
FORCED LUBRICATION TYPE 





DIMENSIONS IN INCHES 








Classification 


Dia. 




Dia. 


Dia. 


Volts 
Full 


Amp. 
Full 


Steam 
Pres- 




Cyl- 

inder 


Stroke 


Steam 
Pipe 


haust 
Pipe 


Load 


Load 


Lb. 


MP 4 -7 -550 


5 


4^ 


IV 


IV? 


110 


64 


80 


MP 4- 8^-550 


5 


4H 


IVa 


IV?, 


110 


/ i 


100 


MP 6-10 -475 


sv?, 


5 


IV 


2 


110 


91 


80 


MP 6-12^-475 


QV?, 


5 


IV? 


o 


110 


114 


100 


MP 6-15 -425 


8 


6 


2 


2V 


110 


136 


80 


MP 6-15 -425 


6 


6 


2 ' 


2Vo 


110 


136 


150 


MP 6-17V 2 -425 


8 


6 


2 


2V 


110 


160 


100 


MP 6-17^-425 


6 


6 


2 


2V 


110 


160 


175 


MP 6-20 -400 


9 


7 


2V? 


3 


125 


160 


80 


MP 6-25 -400 


9 


7 


2 V? 


3 


125 


200 


100 


MP 8-30 -315 


11 


8 


3 


33^ 


125 


240 


80 


MP 8-35 -315 


11 


8 


3 


3V 


125 


280 


100 


MP 6-40 -315 


11 


8 


3 


3 V 


125 


320 


125 


MP 8-50 -280 


12 


11 


3H 


4 


125 


400 


100 


MP 6-60 -280 


12 


11 


sy 2 


4 


125 


480 


125 



Generators can be wound for 110, 125 or 250 volts. 
289 



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292 



therefore, be occasionally run through a filter and mixed with 
new oil. The number of filterings required depends upon the oil 
as well as the length of time the engine operates. 

The oil should stand about % in. above the suction and dis- 
charge valves, and no water should be allowed to mix with it. 
An oil pressure of about 15 lb. should be maintained by regulating 
the adjusting screw of the relief valve. 

Valves 

In all single cylinder engines, the plain plug piston valve is 
employed without any expanding rings. These valves take steam 
through the inner edges, and exhaust past the outer edges. (On 
tandem compound engines the low pressure valves take steam 
through the outer edges and exhaust past the inner edges.) The 
travel of the valve is controlled by the automatic governor; 
varying the cut-off from % to zero, depending upon the load. 
Great care is used in grinding and fitting these valves to their 
chambers, to obtain economical and satisfactory operation. 
The fit of these parts is most important. 

Starting the Engines 

Before steam is admitted to the cylinder see that the valve 
moves freely by turning the governor wheel by hand. As the 
expansion of the valve is much more rapid than the cylinder, the 
cylinder should be allowed to warm up before full pressure is 
applied. By allowing the set to come to full speed gradually, 
no trouble will be experienced due to the valve "seizing." The 
engineer in charge of the section always prepares the engines for 
test, including the adjustment of valves, governors, packing, 
taking of indicator diagrams, care of indicators, piping, con- 
densers and apparatus for weighing water when water consump- 
tion tests are made. 

Tests 

Unless otherwise advised by the Engineering Notice covering 
the particular requisition and engine, all single cylinder com- 
mercial engines are tested for the following only: 

(1) Speed Regulation. 

(2) Steam Consumption. 

(1) The steam and back pressures and electrical load are 
held constant. Then the speed variation is tested by suddenly 
putting on or throwing off load when the conditions are con- 
stant. The total variation between full and no load should not 
exceed 3 Y2 per cent. A speed regulation of 3 per cent is usually 
obtained and at this value the stability of the governing 
mechanism is satisfactory. When adjustments are being made 
for speed regulation, duplicate readings on the generator must 
be obtained, and the voltage must be carefully noted to see if 
it is affected by fluctuation in engine speed. If any voltage 
fluctuation occurs, it must be reported to the engineer and the 
proper correction made. With the engine exhaust connected 
to the condenser, the load must also be thrown on and off and 

293 



the speed noted, especially at no load, to see that the valve 
completely shuts off steam and that the engine does not "run 
away" or "race." 

(2) The performance of every engine must lie within the 
limits given in the tables furnished the Testing Department 
regarding steam consumption. The method of weighing the 
condensed steam is exactly the same as employed on the turbine 
test. The piping in the testing stand and valves is arranged 
so that the exhaust steam from the engine can be passed either 
to atmosphere or through a condenser. If the steam consump- 
tion is excessive, the piston should be examined to see that the 
rings are free in the grooves and that they have a good and even 
bearing against the cylinder wall. If the rings are in good condi- 
tion the valve is probably too small in diameter and allows steam 
to blow directly into the exhaust. In bad cases there will gener- 
ally be a considerable variation in speed as the governor can not 
control the speed, with leaky valves. 

Poor steam economy is generally due to the above causes, but 
lack of lubrication in the steam spaces, excessive friction in the 
stuffing boxes and bearings, or poor valve setting will increase 
the amount of steam used. 

Operation 

During the operation of the set in test the following points 
should be carefully noted: 

(1) Balance of governor pulley. 

(2) Concentricity of crank shaft with armature coupling 
and commutator. 

(3) Absence of oil and grease throwing. 

(4) Operation of engine with reference to quiet running. 

(5) Proper alignment of all parts, especially the crank and 
wrist pin boxes, and central position of piston with reference to 
the cylinder; clearance of oil deflector of armature shaft from 
outboard bearing. 

(6) Oil leakage around ends and at unions of Multiple 
Oiler, and points where supply pipes pass through column on 
gravity lubrication engines ; that the oil drips from supply pipes 
into proper oil cups and channels, and in engines employing 
the forced system of lubrication, the quiet operation of oil pump 
check valves, and of the relief valves and pressure gauge in the 
system. 

(7) The operation and "hang" of throttle valve and align- 
ment of handwheel in reference to the valve stem in engines 
having the valve bolted to the cylinder. 

(8) Absence of leakage in cylinder casting, due to porous 
metal or other causes. 

(9) Fit of oil shields. 

(10) Tightness and adjustment of cylinder relief valves. 
These should be allowed to open at the proper pressure, then 
tighten the set screw in casing about one turn. 

(11) Vibration. 

(12) General appearance of entire set. 

294 



Governor 

The governor used in connection with the gravity lubrication 
type of engines is shown in Fig. 137, and is simpler than the 
various flywheel governors using shifting eccentrics. It consists 
of a heavy flywheel A, keyed to the shaft, and carrying the 
governor weight B, pivoted at C, and containing the eccentric 
D, which operates the valve. 

The governor connecting rod transmits motion from the 
governor to the valve, and is connected to eccentric pin D. 
The length of the valve stroke, therefore, depends upon the 




Fig. 137 
GOVERNOR 



distance of D from the center E. The amount of steam admit- 
ted to the cylinder varies directly as the distance between the 
center of D and E. 

If the engine speed increases, then the weight B is moved 
by centrifugal force toward the perimeter A, decreasing the 
distance of D from the center E and reducing the amount of 
steam admitted to the cylinder. If the speed of the engine 
becomes excessive, the distance of B from E is reduced to the 
minimum and the steam is entirely cut off. 

The motion of the fly weight B is opposed by the spring 
F, which is attached to the pulley and fly weight. By increasing 
or decreasing the tension of the spring, "the speed may be raised 
or lowered. The same effect will be produced by moving the 
spring in the slot of the weight, moving it away from the fulcrum 
increases the speed, and vice versa. 

Unstable regulation is due to too close an adjustment of 
speed, and may be avoided by moving the spring attachment 
away from the fulcrum. A leaking valve or insufficient 

295 



lubrication of the fly weight fulcrum will also produce the same 
effect. If the lubrication is not sufficient the governor should be 
taken apart and cleaned. Only the best of soft grease should be 
used in the cup, and the governor should occasionally be taken 
apart and cleaned to obtain the best results. The governors of 
some of the forced lubrication engines are enclosed by the engine 
column and the bearing pin and eccentric are lubricated by oil 
under pressure from the oiling system. 

Indicator Diagrams 

When indicator diagrams are required, a stud is screwed into 
the wrist pin of the connecting rod for driving the motion, con- 
necting through a link to a lever pivoted to the bracket on the 
engine column. The motion for the indicator is taken from a 
cord pin on this lever. 

The indicator is a delicate instrument, and must be handled 
with care and kept in good order. The piston springs should be 
frequently calibrated. Before attaching the indicator to an 
engine, blow steam freely through the pipes and three-way 
cock to remove any particles of dust or grit that may have 
accumulated in them. After being used, the indicator should be 
carefully wiped and oiled. If any grit or other obstruction gets 
into the cylinder of the indicator the diagrams will give wrong 
results. This trouble is easily detected and should be remedied 
at once by taking out the piston, detaching it and cleaning with 
oil and replacing. The piston must move perfectly freely in its 
cylinder. To test this, take out the piston and spring, detach 
the latter and replace the piston and piston rod in their operating 
position, then, holding the indicator in an upright position, 
raise the pencil arm to its highest point and let it drop. It should 
freely descend to its lowest point. 

Before taking diagrams, steam should be admitted to the 
indicator, and the cylinder allowed to become thoroughly heated. 
Indicator springs are made in different sizes of steel wire, to 
adapt them to different steam pressures. Springs are usually 
made to the following scales: 8, 12, 16, 20, 30, 40, 60, 80 and 100 
pounds per inch travel of the indicator pencil. This scale is 
stamped on the spring. The spring used for indicating an 
engine depends upon the maximum steam pressure used; a 
spring should be chosen to give a diagram with maximum height 
not exceeding 1% in. The diagram should not exceed 2 3^ in. to 
3 in. in length. The less the vertical and horizontal motions 
are, the slower will be the movement of the paper cylinder with 
a correspondingly more delicate pencil tracing. The proper 
spring required may be found as follows: Divide the boiler pres- 
sure, expressed in pounds, by the desired height of the diagram, 
expressed in inches, and the result will be the spring required. 
For instance, with a boiler pressure of 140 lb. gauge and a 
diagram height of 1 % in. then 140 ■*■ 1 % /± = 80, is the number of 
the spring required. 

If too weak an indicator spring is used it will vibrate inside 
the indicator cylinder at admission and cause a wavy line on 

296 



the card, hence the strength of the spring should be chosen with 
due regard to this point. The indicator cord should have 
sufficient tension on it to prevent any whipping action occurring 
at the extreme point of the stroke. Hence sufficient tension 
must be given to the rotary spring in the indicator to prevent this- 



Cor-r-cj&cttec/ 
Copper- GosHet, 



g waste f=>/p>e &r>c/ Vo/ve 




Fig. 138 
PISTON ROD PACKING 



action. If the tension on this spring is not sufficient, the length 
of the indicator cards will vary; the higher the speed of the 
engine the greater will the variation be. 

The pressure of the pencil upon the paper can be adjusted 
by screwing the handle in and out. The line should not be 
heavy as this will cause unnecessary friction. After the diagram 
has been taken, close the cock and take the atmospheric line; 
then disconnect the cord to avoid excessive wear on the drum. 

297 



The following notes should be made on the card and any- 
other data which it is proper to add: 

Date Time 

Requisition No. Dia. of Rod 

Kw. Capacity Cylinder 

Card No. Boiler Pressure 

Stroke Exhaust Pressure 

Clearance Revolutions per min. 

Scale of Spring Volts 

Engine No. Amperes 

Cylinder No. Pounds of water per kw-hr. 

Dia. of Cylinder 

A trifle more lead at the crank end of the valve should be 
given at no load, as at % or full load the average pressure on 
either side of the piston will be found to be. practically equal, 
due to the angularity of the connecting rod. Various adjustments 
will be necessary to obtain the best diagram and operation of the 
engine. 

Packing 

In all single cylinder engines, up to and including the 30 kw. 
size, the Garlock Spiral Packing is used in both piston rod and 
valve stem stuffing boxes, and in the valve stem stuffing boxes 
of all engines, the leakage being taken up by tightening the brass 
nut on the box. 

In the piston rod stuffing boxes of the tandem-compound, 
cross-compound and of the single cylinder 50 kw. engine, 
United States Metallic Packing is used. Fig. 138 shows the 
"Double" type which is commonly used, but in some machines 
the "Single Junior" packing is employed. The general con- 
struction of the two packings is similar. 

The packings consist of vibrating cups A and A , receiving the 
packing rings 1, 2 and 3. These rings are in halves and, in assem- 
bling the packing, the joints should be broken. The vibrating cups 
rest upon rings B and B, which have a spherical bearing, so that 
the packing will follow the rod in any position. The steam 
pressure forces the packing down in the cups and against the 
piston rod, thereby preventing steam leakage. The coil springs 
C and C assist this pressure, at the same time holding the pack- 
ing in place and preventing the rings from following the rod at 
the moment of reversing. If the packing has been taken out for 
examination, the ground surfaces should be cleaned and freed 
from grit before reassembling. The box holding the packing 
is drilled and tapped for a % i n - waste pipe and fitted with a 
globe valve which should always be open. 

General Instructions 

An engine unit should not be considered mechanically nor 
electrically perfect, until the tests have so proved. Testers 
should familiarize themselves with every detail of design and 
operation, thereby helping toward the production of the most 

298 



reliable piece of apparatus. After the inspection in the Engine 
and Testing Department the unit is dismantled and thoroughly 
overhauled, touched up and re-inspected, preparatory to final 
shipment. 

GENERATOR 

The tests taken on the generator are duplicates of those 
described in preceding chapters. All standard d-c. generators 
are given only compounding tests and adjustment of shunts. 
On standard a-c. generators saturation and synchronous imped- 
ance are taken. 

If core losses are called for they are taken as previously 
described, the generator being either disconnected from its engine 
and assembled in shop bearings or the connecting rod, etc., 
of the engine is dismantled and a driving belt slipped over the 
engine flywheel. 



299 



CHAPTER 15 

GENERAL ELECTRIC TEST TRACKS 

As the work on the General Electric Test Tracks is almost 
entirely experimental a large number of the tests require special 
instructions. The following rules, however, have been issued 
relative to the operation of trains on these tracks, as well as 
instructions for obtaining data, in testing apparatus. 

No test should be started nor should changes be made in any 
test without instructions from the office of the Supervisor of 
Test Tracks. 

All data should be recorded upon special record sheets and 
supplementary column sheets, or upon the special form sheets 
provided for that test. 

All data sheets should contain the name of the man in charge 
of the test, and date of test, while all supplementary column 
sheets should also contain in the upper right hand corner the 
number of the record sheet to which they belong. 

ELECTRIC LOCOMOTIVES 

Special form sheets are printed for testing locomotives, which 
should be carefully filled out. The procedure of testing is as 
follows : 

1st. Inspect motors, contactor compartments, rheostat 
compartments, controllers, etc., for loose material, scrap wire, 
etc. Examine all bearings to see that they are properly lubri- 
cated, including motors, air compressors, dynamotors and all 
operating parts. 

2nd. Ring out wiring to see that all connections are accord- 
ing to the wiring diagram. Inspect the wiring to see that all 
terminals are properly soldered and secured with lock washers; 
also that all parts of both the main and auxiliary circuits are 
properly insulated and that all wiring is so secured as to prevent 
the insulation being cut by chafing. 

3rd. Take clearance measurements to see that the locomo- 
tive conforms to the clearance diagram. 

4th. See that the current collecting devices are in proper 
condition and satisfactory for operation. 

Where third rail shoes are used this should include the 
pressure on the rail in the running position as well as the measure- 
ments showing the position of the shoe with respect to the third 
rail. 

On trolley poles and bases it should include the pressure of 
the wheel on the wire at some given angle of the trolley pole. 
This can be taken with a small spring balance attached to the 
trolley rope. It is well to note what this pressure is, both going 
up and coming down, to insure that the base does not have an 
undue amount of friction. 

On pantograph trolleys the pressures of the pans, or rollers, 
against the wire should be taken as on trolley poles and wheels. 
Where rollers are employed as collecting devices it should be 

300 



carefully noted -whether the rollers are free to revolve and whether 
they are in every way satisfactory to operate. 

5th. Connect to the power circuit and try out the lighting 
circuit, including headlights. Pump up the air pressure and 
try out the air brakes, adjust all valves, gauges, etc., according 
to the air brake diagram and inspect all air piping for leaks. 

6th. Check with the wiring diagram the contactors that 
are closed, both forward and reversed on each notch of one 
controller and if there are two controllers check in one direction 
of the second controller. For some typical connections see DS 
prints No. 15466, 28765, 28234, 29302, 39188. These prints 
are on file in the Testing Section office. 

7th. Determine the rotation of the motors, each motor or 
pair of motors separately and with all motors cut in. This 
should be done in both directions on each combination. 

8th. Measure the resistance of each step of the starting 
resistance to see that it agrees with the specification. This 
should be done by applying the air brakes so that the locomotive 
does not move and having an ammeter wired in the motor 
circuit. Put the controller on the first point with the main 
switch closed so that the current will pass through the motor 
circuit. Simultaneous readings should be taken of the current 
flowing and the voltage drop across the various steps of resist- 
ances. The voltmeter leads should be applied at the con- 
tactors, or controller fingers to which the resistances are attached 
in order to make an additional check on the wiring. Care should 
be taken not to keep the current on longer than is absolutely 
necessary to take each reading so as to avoid an increase in 
resistance due to heating. 

9th. Where a blower is used for forced ventilation of the 
motors the distribution of air to the different motors should be 
taken, holding constant the voltage of the trolley and reading 
volts line, amperes input to the blower motor, speed of the 
blower motor and the air pressure at some given point on the 
motor so that the volume of air going through the motor can be 
obtained by comparing these results with the result of tests 
previously made on the test stand. Before starting this test an 
inspection should be made to make sure that all motor covers 
are on, air outlets from the motors open and that the air inlet 
and outlet of the blower are free from any obstruction. 

10th. Run for tests on bearings and note the operation 
of all auxiliary parts. This test should be started at slow speed 
and the speed increased as soon as the temperature of the 
bearings will permit, to the maximum speed at which the 
locomotive is to be run and continued at this speed for several 
miles, or until the bearings and all operating parts are in satis- 
factory operating condition. 

11th. Make a wheel slipping test by bringing the controller 
up, point by point, until the wheels slip and read volts line and 
amperes to the motor on each step of the controller. This test 
should be made in both directions with and without sand and 
with all the various combinations of motor cutout switches. 

301 



It is necessary to take readings on each point, beginning with 
the first, only once for each combination and after this the 
controller should be immediately brought to the point next 
below the one at which the wheels slip and readings taken at this 
point and continued as before until the wheels slip again. The 
controller should be thrown off as soon as the wheels start to 
slip so as to damage the track as little as possible. The wheels 
should not be allowed to slip more than once in the same spot 
otherwise a false indication of tractive coefficient might be ob- 
tained. 

12th. Remove all grounds and take insulation and high 
potential test. These should include all the wiring and all 
parts of the electrical equipment. 

Mounting Motors on Trucks 

Before mounting motors on trucks, the following measure- 
ments should be taken: Compare bore of gears with size of 
axle for gears ; compare bore of axle liners with size of axle for 
liners ; compare the distance between wheel hubs with the length 
of the motor; axle liner flanges and gear hub; compare the 
distance between the center of axle and suspension bar face on- 
truck with the distance between the axle box centers and face 
of motor under nose suspension. 

After these dimensions have been checked, and the motors 
have been found to fit on the truck, the key for the gear should 
be fitted in the key- way and the gear put on, care being taken 
to get the right side of the gear next to the hub of the wheel, and 
to see that all lock washers and cotter pins are in place. The 
motor should then be hoisted by the two lugs opposite the axle 
bearings with a two hook chain, and the motor placed on the axle 
without axle linings. The motor can then be lowered in place, by 
allowing it to revolve around the axle until the nose suspension 
rests on the suspension bar. The chains can then be hooked 
in the two lugs nearest the axle bearings and raised enough to 
allow the axle linings to be put in place. The axle caps, gear 
cover and strap fastening the motor to the suspension bar can 
then be put on and the installation is complete. 

Before the motors are put into service or the car run as a 
trailer, the motor bearings and gears should be properly lubri- 
cated. 

Trolley Bases 

Test sheets should contain the following data: 
Number and size of spring (outside diameter, free length, 
number of turns and size of wire). Position of tension adjusting 
screw during test. Length of pole from pivot to center of 
trolley wheel. Style of harp and wheel. Length and tension of 
springs with pole, in horizontal and 45 degree positions. 

Pull Curve 

This curve is taken by measuring the vertical pull in pounds 
at the center of the trolley wheel for different heights of the wheel. 

302 



The "height" of the wheel is the vertical distance of the center 
of the trolley wheel above its position when the pole is hori- 
zontal. (For pantograph trolleys the height is the distance of 
the top of the pan above its position when locked.) In taking 
this test a rope should be fastened about the wheel and readings 
of pounds pull taken, both going up and coming down. 

Service Heat Runs on Motors 

These heat runs are made on motors under as nearly as 
possible the same conditions as will obtain in service. By 
making a number of heat runs under various conditions data is 
obtained from which the thermal characteristics of the motor 
are determined. These curves show the relation between the 
ratio of distribution of losses (ratio between watts loss in field 
and in armature) to the degree (Centigrade) rise per watt loss 
for the armature and for the field. 

The instructions for the test include the following points: 

(a) Weight of train. 

(b) Line voltage to be held. 

(c) Accelerating current required. 

(d) Schedule (includes length of run, time power is on, 
time of coasting, time of braking, and time of lay-over). 

The following readings must be taken before starting the 
test: Resistance of field, total and partial. resistance of armature. 

In order to facilitate the measurement of armature resist- 
ance during the run, resistance readings are taken between 
commutator bars nearer to each other than the distance between 
brushes. These bars should be marked or the resistance taken 
with a templet, in order that all measurements can be made 
between the same points or including the same number of bars. 
The ratio between the partial resistance to the total resistance is 
a constant from which the total resistance can be calculated. 

The following must also be taken during the test: 

Air temperature, velocity and direction of wind, readings 
during test (taken every hour), field resistance, partial resistance 
of armatures of alternate motors, temperature by thermometer 
of field spools and frame, and air temperatures. 

During the run a record is kept of the schedule, direction of 
wind, weather conditions and all points of any interest in 
connection with the runs. 

Records of the line voltage and amperes motor are taken 
with graphic recording meters for a couple of runs in each 
direction during the hour. 

When the temperatures of the motors have become constant, 
the test is stopped. Besides the regular hourly readings the 
following temperatures are taken: Armature core surface, and 
conductors; commutator; field spools; frame. 

These readings should be taken indoors in order to avoid 
all draughts. 

Train Friction 

Train friction curves show the relation between the train 
or car friction expressed in pounds per ton and speed in miles 
per hour. 

303 



There are two methods by which car friction may be obtained, 
coasting tests and free running. 

Friction from Coasting Curves 

The. test should be made on a straight and preferably level 
track. The car is accelerated to a speed slightly greater than 
the highest speed called for on the friction curve and allowed 
to coast. Speed should be measured with a speed recording 
instrument. Runs should be made in both directions. 

From the rate of retardation at any point the retarding 
force is calculated which represents the total car friction at that 
speed. 

The weight of the car plus the flywheel effect of the revolving 
parts is the weight that tends to keep the car moving. When 
geared motors are used, a test should be made to obtain the rate 
at which the armature will slow down due to the friction of its 
own bearings in order that it may be known whether the flywheel 
effect of the armature will be sufficient to overcome the friction 
of its own bearings and furnish power to assist in keeping the 
car moving, or whether the car will have to furnish power to keep 
the armature revolving. The type of motor and the gear ratio 
should be given, together with any information that can be 
obtained, regarding the type of car, arrangements of wheels, 
wheel base of truck, etc.; if possible a photograph, or a sketch 
showing the cross section of the car, or locomotive should be 
included. 

Friction by Free Running 

With the car running at constant speed, readings of speed, 
volts line and amperes should be taken, preferably with graphic 
recording meters. The input to the motors, minus their elec- 
trical losses, gives the power absorbed in friction at a given 
speed. 

It is very difficult to get accurate results by this method on 
account of the difficulty of keeping the car speed absolutely 
constant. 

The test sheets should contain the following data: 

Weight of car or train. 

Diameter of wheels and speed of car. The number, rating 
and serial numbers of motors, and gear ratio, must be given. 

Operating Rules 

Each man, when starting work on the Test Tracks, is given 
a copy of the "Operating Rules." These must be carefully 
learned and implicitly followed at all times. 



304 



CHAPTER 16 

BLOWERS 

Commercial Tests consist of the operation of the blower 
for such a length of time as is necessary to demonstrate that no 
electrical or mechanical faults exist. In case the motor is of 
sufficient power to drive the fans with unrestricted inlet and 
outlet it is so tested, but in most cases the motor is provided 
for a certain specified pressure and volume delivered from the 
fans and will not operate the fan with unrestricted inlet and 
outlet without overloading the motor. In such cases the load 
on the motor can be limited by partially obstructing the inlet to 
the fan by means of a blower or other restriction so that the motor 
will not be subjected to an excessive load. 

Standard Heat Run consists of the operation of the 
machine with air delivery restricted for a specified time or until 
constant temperatures of the motor are reached. This restriction 
may be for the purpose of bringing the load on the motor to a 
specified amount or may be a restriction to give the required air 
delivery for which the fan is to be supplied. 

Minimum Speed Heat Run consists of a heat run at full 
field with unrestricted inlet and outlet for a specified time or 
until constant temperatures are reached. 

Maximum Air Delivery Heat Run consists of operating 
the blower at full speed with the inlet and outlet unrestricted 
for a specified time or until constant temperatures of the motor 
are reached. 

Endurance Run consists of running the machine for 48 
hours with the specified restriction of blower inlet and outlet. 

In case of ventilating fans for the Government, this consists 
of a 40 hr. run in addition to the 8 hr. " Normal Air Deliverv Heat 
Run." 

General Tests consist of the following: 

(a) Running the machine with air delivery restricted for a 
specified time, or until constant temperatures of the motor are 
reached. 

(b) 48 hr. endurance run (40 hr. in addition to the normal 
air delivery heat run). 

(c) Heat run at full field with unrestricted inlet and outlet 
for a specified time, or until constant temperatures are reached. 

(d) Air measurements to determine the delivery of the 
blower. 

Special Tests consist of general tests on the blower to 
obtain air delivery under different conditions of opening and 
under different speeds. 

Complete Tests consist of the following: 

(a) Running the machine with air delivery restricted for 
a specified time, or until constant temperatures of the motor 
are reached. 

(b) 48 hr. endurance run. 

305 



(c) Heat run at full field with unrestricted inlet and outlet 
for a specified time, or until constant temperatures are reached. 

(d) Tests on the blower to obtain air delivery under differ- 
ent conditions of opening and under different speeds. 

1. DOUBLE PITOT TUBE OR GOVERNMENT METHOD 

This test is made in accordance with Government specifi- 
cations issued by the Navy Department under the cognizance 
of the Bureau of Construction and Repair. 

For making air tests in accordance with this method using 
double Pitot tubes, a testing pipe preferably of galvanized iron 
having the same shape and size as the outlet of the fan and a 
length equal to twenty times the diameter of the pipe, if round, 
or twenty times the average of the width and depth, if rectangu- 
lar, should be connected to the fan outlet. This pipe should be 
smooth and carefully fitted to the fan in order to avoid any 
unnecessary obstruction to the free passage of the air. 

It is sometimes inconvenient to use a pipe of exactly the same 
shape as the fan outlet, and in many cases it would be permissible 
to use a pipe of nearly the same area connected to the fan outlet 
by an adapter gradually changing from the size of the outlet 
to the size of the pipe. 

The double Pitot tubes should be supported in the middle 
of the test pipe half way between the two ends and should 
be parallel to the sides of the pipe and pointing toward the fan. 
All connections between the Pitot tube and the Manometer or 
U-tube should be carefully made to avoid any possible leakage, 
as a very small leakage in the connections of these rubber tubes 
might seriously affect the reading of the manometer. 

In making the measurements the exact area of the pipe 
where the Pitot tube is located should be carefully measured 
allowing for curvature of the sides of the pipe which sometimes 
takes place when the pipe is made of thin material and the pres- 
sure in the pipe is considerable. When the area of this pipe differs 
from the area of the outlet of the fan, the results should be 
corrected accordingly, as the air velocity will be greater in a 
smaller pipe and the static pressure less, but the total impact 
pressure will not be affected except by the increased friction 
of the smaller pipe. 

A suitable damper or door should be placed at the end of the 
testing pipe so that the size of the opening may be adjusted 
to obtain the proper pressure and volume. Care should be taken 
to run the fan at rated speed as nearly as possible, but where 
this is impracticable, correction may be made for small varia- 
tions in speed by correcting the volume in proportion to the 
speed and the pressure in proportion to the square of the speed. 

The most accurate results are obtained by using a nest of 
Pitot tubes connected to floating manometers which consist of 
metal cans floating in water, divided into as many air tight 
compartments as there are Pitot tubes ; but it is more convenient 
to use a single tube in the middle of the pipe, in which case, 
according to the U.S. Navy rules, the velocity determined by 

306 



the Pitot tube should be divided by 1.10 to obtain the assumed 
average velocity through the whole pipe. 

In calculating the horse power the total impact pressure 
is used without any reduction, although to be strictly consistent 
the velocity head due to the average velocity of the pipe added 
to the static pressure should be used. 

When the blower is provided with a straight inlet a con- 
siderable loss is occasioned by vena contracta which will not take 
place when the inlet piping is finally installed on the fan. If 
the fan were tested with nothing added to the inlet, the efficiency 
shown by the test would be too low and it is desirable to put 
a short cone or bell on the inlet of the blower in making the 
efficiency test unless the fan is built with a cone inlet. 

Use of Air Table 

When conducting a fan test the temperature of the air in 
the testing room should be taken by two Fahrenheit thermom- 
eters, placed near the fan. One should hang free in the air, and 
the other, with its bulb wrapped in thin cloth, should be sus- 
pended over a small receptacle filled with water so that the cloth 
will be saturated. The temperature of the water must be the 
maximum that it will naturally attain in the room, Corrected 
barometer reading must also be recorded on the test sheet. 

The method of finding the weight of air from the air tables 
mentioned in the specifications, is as follows: On the page 
containing the dry bulb reading as recorded on the test sheet, 
note the barometer reading corresponding to the first three 
figures of the corrected barometer reading recorded on the test 
sheet. In the column under the dry bulb temperature and 
opposite the barometer reading, the corresponding weight of 
saturated air is given. The weight of air found in the table must 
then be corrected to correspond with the corrected barometer 
reading found in test. This correction will be found in the second 
line from the top of the page. Correction must also be made for 
the difference between the wet and dry bulb temperatures by 
adding to the weight of air already obtained the number in the 
third sub-division of the column under the dry bulb temperature 
which corresponds to the difference between the wet and dry 
bulb reading. This reading will be found in the second sub- 
division of the column. 

Example 

Given barometer reading 30.15 in. 

Dry bulb reading 67° F. 

Wet bulb reading 59° F. 
Under the column showing the dry bulb temperature of 67° 
and opposite the barometer reading of 30.1, the weight of air 
is given as 0.07517. The addition for each 0.01 of an inch of 
barometer is given as 2.6 in the second line from the top of the 
page. Multiply this by 5, i.e., by the excess of the corrected 
barometer reading over that selected in the table; the result 
is 13, which must be added to the weight of air previously found. 

307 



The wet bulb depression is the difference between 67° and 59°, 
or 8°. The number opposite 8 is 23. This must also be added, 
making the total weight of air 0.07553. All pressure readings 
should be corrected for standard air (see page 309) by multiplying 
the actual pressure obtained by the ratio of the weight of standard 
air to the weight of air at the time of test. The readings of horse, 
power input to the fan should also be multiplied by this ratio. 
Pressure and Horse Power Curves by Double Tube Method 

A pressure curve may be taken by the double tube method 
as follows: 

The opening at the outer end of the discharge pipe should 
be closed and pressure and power readings taken. Under this 
condition the static and impact pressures should be exactly the 
same since no air passes through the fan. Readings should then 
be taken by increasing the opening by suitable increments from 
closed to wide open, measuring the opening each time. The 
speed of the fan should be held constant throughout the test. 
The air readings and electrical input readings should be taken 
simultaneously. 

It will be noted that in a test which is made with a pipe 
on the discharge side of the fan, the reading of the impact tube 
is always greater than the static reading. If the pipe is on the 
suction side the readings will be negative and the greater numeri- 
cal value will be given by the static side of the tube. This 
should be considered as the value for impact pressure of the fan. 
The smaller value is given by the impact tube and should be 
treated as static pressure when considering the capacity of the fan. 

If readings are taken by means of a U-tube, the reading of 
both sides of the tube should be given on the test sheet. The 
test sheet should always specify whether the readings were 
taken by the U-tube or by a manometer. If by a manometer, the 
manometer constant should be recorded and must always be 
used in working up the test. 

CALCULATION OF FAN TESTS BY THE DOUBLE TUBE METHOD 

A fan test of this kind should be recorded in the following form 
of the standard column paper provided for this purpose. The same 
abbreviations should always be used to avoid confusion. 

TYPE OF FAN SERIAL NUMBER DATE... 

Motor Rating 

Double Tube Test, Taken at R.P.M. 



No. 


hi 


hi 


h 3 


*S 


V 


Q 


hl+hf 


ht+h f 


Air 
H.P. 


Fan 
H.P. 


EfL 


1 
2 
3 
4 
















I 







Wet Bulb °F. Barometer... ....in. 

Dry Bulb °F. Wt. of Air lb. 

Effective area of Pipe = Sq. Ft. 

308 



The first column gives the number of the reading. 

The second and third show the impact and static readings 
taken from the test sheet and corrected for standard air. 

The fourth column shows the velocity head or the difference 
between hi and h 2 . 

The fifth column is friction which must be calculated from 

the velocity head bv the formula H = ^- X 0.000 16 lv 2 . 

ab 

TT 

hf= w?r-^, where h/ equals friction loss in inches of water, / is 

oy./o \ 

the length of pipe in feet between the fan and the Pitot tube. 

a = length of long side of pipe in feet. 

b = length of short side of pipe in feet. 

i» = average velocity in feet per second. 

The friction loss should be added to both the static and 
impact readings before the curves are plotted, but it does not 
affect the volume. 

The sixth column showing the air velocity at the center of 
the pipe may be obtained from the curves shown on prints 
C-4487-A, B, C, and D. It may also be obtained from the 

formula V=1097-*|— 

Where to = weight of air per cu. ft. in pounds. 

This gives the velocity at the center of the tube. For the 
average velocity use 91 per cent of this value or use the same 
formula with a constant of 997 instead of 1097. 

The volume must be given in the seventh column. It is 
obtained by multiplying the average velocities given in column 
six by the area of the pipe. 

The horse power in the air can be calculated from the formulas 

.. , PXQ PXQ hXQ 

Air h ' p - = 33000 ° r 3667 ° r 6345 . 

The horse power input to the fan is the horse power output 
of the motor. 

Unless instructions are issued to the contrary, all fan tests 
for Government work should be plotted with pounds per sq. ft., 
horse power input to fan, and efficiency as ordinates; and volume 
in cu. ft. per minute as abscissae. Both static and impact pres- 
sure should be plotted. 

The tester should carefully date and sign each test sheet, 
and should include sufficient data to distinguish all sheets used 
on the same test. For instance, electrical readings are usually 
placed on one sheet and fan pressure readings on another, 
therefore, each of these sheets should state the name and number 
of the fan, the rating of the motor, the speed at which the test 
was taken and the method used. The Calculating Room must 
see that this data is placed on the Calculation Sheet. 

The sheet on which the curves are plotted should give the 
name, type and number of fan, rating of the motor, speed at 
which the test was taken, and the method employed. Curves 
should always be plotted across the width of the sheet. 

309 



2. CONE METHOD OF TEST 

The following method of conducting a fan test is used only 
when a short convenient method is required for purposes of 
comparison. In this method of test an adapter is used, where it 
is necessary, to change the fan outlet from rectangular to cir- 
cular, a cone being placed on the circular end. This cone is 
made up of sections about two feet in length, the sides of which 
slope about two inches to the foot. Readings are taken by a 
single Pitot tube, the open end of which is held flush with the 
opening in the outer end of the cone and pointed against the 
stream of air. Pressure is registered as before, by a manometer 
or U-tube. The readings are taken, one at the top, one at the 
bottom, and one at each side of the cone at a distance from the 
edge of the pipe of about % of the diameter of the opening. 
A reading is also taken in the center of the cone opening. The 
average of these five readings represents the impact pressure 
produced by the fan, and is taken as the velocity head. The 
velocity may be obtained from the curve or from the formula 
given for the double tube test. 

The static pressure may be obtained as follows: Divide the 
volume of each opening by the area of the fan opening, which 
gives the outlet velocity V\. The corresponding velocity head 
can then be obtained from the curve. The velocity head sub- 
tracted from the impact pressure gives the static pressure. 
The static pressure should be plotted as well as the impact 
pressure. 

These tests should be plotted with pressures in inches of 
water, h.p. inputs to the fan, and efficiencies, as ordinates; and 
volumes as abscissae. 

The following form should be used for tabulating the results 
of calculations: 

TYPE OF FAN SERIAL NUMBER DATE 

Motor Rating 

Cone Test Taken at R.P.M. 



No. 


hi 


V 


Ae 


Q 


Vi 


h s 


hi 


Air 
H.P. 


Fan 
H.P. 


Eff. 


1 
2 
3 























Wet Bulb °F. Barometer in. 

Dry Bulb °F. Wt. of Air. lb. 

After the curves are plotted, the efficiency, as given by the 
calculations, should be checked, with the efficiency obtained 
from the curves. This will correct any discrepancy between 
the efficiencies as obtained from the curve and as calculated. 

310 



3. THE BOX METHOD 

The box method of testing fans is as follows: 

The fan is arranged to discharge directly into a large box 
which has a sufficient capacity to reduce the air velocity to 
a minimum. An opening is made in the side of the box at right 
angles to the opening into which the fan discharges, and cones 
are attached similar to those used in the cone test. Readings 
are taken by the same method and readings should also be 
taken of the box pressure by a U-tube connected to a pipe 
inserted through a hole in the side of the box. The end of the 
pipe should be flush with the inside of the box to avoid eddy 
currents. The pressure shown by this pipe will be somewhat 
higher than that registered at the end of the cone, and both 
pressures should be corrected for standard air and plotted on the 
final curve sheet. 

The volume must be calculated as in the cone test, but the 
pressure obtained in the box is taken as the static pressure 
produced by the fan, since the velocity head is lost in the box. 
To obtain the impact pressure the volume obtained should be 
divided by the area of the opening of the fan, and the cor- 
responding velocity head taken from the curve. This velocity 
head should be added to the static pressure shown by the cone 
readings. For transformer ventilation it is customary to calculate 
the pressure in ounces, measured at the cone opening. 

The following form should be used in tabulating the calcula- 
tions: 

TYPE OF FAN SERIAL NUMBER DATE 

Motor Rating... 

Box Test Taken at R.P.M. 



NO. /J2 


P v 


Ae 


Q 


Vi 


hz 


hi 


Air 
H.P. 


Fan ' -pa: 
H.P. btt - 


1 

2 
3 

4 





















Wet Bulb °F. 

Dry Bulb °F. 



Barometer in. 

Wt. of Air..... lb. 



Fan h.p. should be calculated from the static pressure and 
the efficiencv obtained will be the static efficiencv. 



FORMULAE FOR BLOWER TESTS 

h\ = Impact head in inches of water. 

h 2 = Static head in inches of water. 

h 3 = Velocity head in inches of water — hi — hi. 

h= Total head in inches of water =/*i+ Ay 

w = Weight of air in test in pounds per cu. ft. 

311 



B = Barometer reading. 

h f = Head lost in friction in the pipe from the Pitot tube to 
the fan, in inches of water. 

H/ = Head lost in friction in the pipe from the Pitot tube to 
the fan, in feet of air. 

Hz = Velocity head of the air in feet of air. . 

a = Length of long side of pipe in feet. 

b = Length of short side of pipe in feet. 

/ = Coefficient of friction =0.00008 for ordinary piping. 

This value should be used in determining the friction loss 
between the fan and Pitot tube, but for determining the amount 
of pressure required to overcome the resistance of air piping, 
it is usually safer to use a coefficient of 0.00010. 

I = Length of pipe in feet from Pitot tube to fan. 

v = Mean velocity of air in ft. per sec. 

V = Velocity of air in ft. per min. 

Q = Volume of air in cu. ft. per min. 

P = Pressure of air in lb. per sq. ft. 

. -p , . . . PX16 P 

p = Pressure of air in ounces per sq. in. = . = -^. 

A =Area of pipe in sq. ft. 

A e = Effective area of pipe in sq. ft. =A XK 

K = Constant for effective area of pipe =0.94 for the Cone 

Method. 
Eff = Efficiency. 

w = Weight of air in test in pounds per cu. ft. 
Weight of 1 cu. ft. of air at 30 in. Bar; 70 deg. F and 70 
per cent humidity = 0.07465 lb. 
This is taken as standard air. 
Wefght of water = 62.36 lb. per cu. ft. at 62 deg. F. 

Weight of a column of water 1 ft. sq. and 1 in. high = ' 

= 5.2 lb. at 62 deg. F. 

Weight of a column of standard air 1 ft. sq. and 1 ft. high 
= 0.07465 lb. 

Weight of a column of any other air 1 ft. sq. and 1 ft. high 

= w. 

xt 1 x- 1 .j-x 0.07465X5X530, ^ u 

Neglecting humidity w = 30X ( 46 q +1 o j for Fahr - 

at i ,■ i. ■/■, 0.07465X5X294, _ , 

Neglecting humidity w = 30 x (273 +^ °)~ 

Therefore, to change from feet of air to inches of water 

5 2 
divide by - _ ' Anr =69.73 for standard air. 
0.0/465 

5 2 

or divide by — — for any other air. 
w 

H f 



hf= 5.2 



312 



ab 
For round or square pipe JHy-=4/-j- o 2 

where d = diameter in feet. 

/ / — Jo. 2 hz \hz 

v =\/2 ^ 3 = 8.02 \ Hz= 8.02 J— ^~ = 18.28-J- 

F =60 f=60v2 £# 3 =481.2\/#3 

= 1097 —at the center of the pipe. 



$"'« 



= -i015\/liz for standard air. 
P =9 p 

= o.2Xh 
Therefore 9 p=5.2Xh 

P = IT32 = °- 577 * 



<2 =rx.4,= Fxxi 

av. vel. I . 
= 0.94 J 



Ihz =3654.0 A \/hz, using <x 

= 1097 A -X^4 ___//_!' * _ ^torstd.air 
\ -' = 3774.0 A \/hz for K 

For a given opening, pressure varies as the square of the speed 
of the blower. Volume varies as the square root of the pressure, 
hence, directly as the speed, 

Air h.p. varies as the cube of the speed. 

Eff. = *£*& 

Fan h.p. 



313 



CHAPTER 17 

AIR COMPRESSORS 

Wearing in Running 

The air compressor should be run unloaded,- that is, not hav- 
ing the delivery end of the compressor connected to the tank 
until the friction has reached a constant value. 




Fig. 139 
AIR COMPRESSOR 

Commercial Test 

Resistance measurement should be made. The compressor 
(see Fig. 139) should be run light and the voltage, current and 
speed noted and recorded. The friction value should be checked 
with that given in the Standing Instructions (S. I.) 7884 and 
if it is excessive the defect must be remedied before the test 
is continued. 

A full load run should be made for a half hour or an hour as 
specified by the Standing Instructions during which three suc- 
cessive capacity tests should be made in the following manner: 
The compressor should be connected to tank No. 1, see Fig. 140. 
The gauge .pressure in tank No. 1 should be brought to 90 lb. or 
other standard working pressure as specified and the air then led 
into tank No. 2 at such a rate that the specified working pressure 
is maintained on tank No. 1. Note should be made of these 
items; the time from the opening of the valve between tank No. 
1 and tank No. 2 until the gauge of tank No. 2 shows that work- 
ing pressure has been reached; the total armature revolutions 
(on the testing record this should be reduced to compressor 
revolutions); the current required; the temperature of the air 
in tank No. 2 and the temperatures on the compressor cylinders. 

The high potential test should be made at the end of the run 
with the motor hot. The oil leakage indicated by the glass gauge 

314 



should be noted and also the air leakage of the compressor 
valves after the end of the test. 

All compressors should be carefully observed for unnecessary 
noise or vibration in operation due to gears, connecting rods, 
valves or unbalanced armature. They should be observed for 
air leaks due to porous cylinder heads and defective gaskets and 
valve plugs; for oil leaks due to defective crank chamber 
gaskets or porous castings, for oil leaks entering the inner end of 
the motor frame from the compressor frame, and for vapor 
escaping from the crank chamber vent. If defects are found they 
must be reported at once. 

Complete Tests 

Complete tests consist of special tests, special heat runs, 
starting tests, and oil leakage tests. 



Thermometer 



Exhaustin 
8hop Line 



\Safty 
waive 




Gauge 



Gauge 
Exhaust under ... JLL (F^ 




Compressor ~~W 



Fig. 140 
TANK CONNECTIONS FOR AIR COMPRESSOR TEST 



Special Tests 

A speed curve should be taken in the operating direction of 
the compressor only, at 600 volts unless otherwise specified, on 
compressor loads in which the tank pressure varies from zero to 
140 lb. During this test, or by making an independent test, the 
capacities of the compressor should be taken while pumping 
against pressures varying from zero to 140 lb. From these tests 
one curve should be plotted of tank pressure and compressor 
speed against amperes as abscissae. Another should be plotted of 
watthours per cu. ft. of free air and cu. ft. per minute of free air 
against tank pressure. 

315 



The field of the motor should now be separately excited, 
the gears removed and the friction and motor core loss test 
taken. 

The armature should be run on a voltage which will give. a 
speed corresponding to the speed curve and the field should be 
separately excited with the same current values as used when 
the speed curve was taken. A curve is then plotted of watts 
against rev. per. min. showing the friction and core loss com- 
bined. 

The preceding results should be consolidated into a curve 
showing the speed, torque and efficiency of the motor at the 
pinion. 

Special Heat Runs 

These consist of several heat runs made with the compressor 
operating at different time cycles and different pressures. 
Usually three successive tests should be made at the rated work- 
ing pressure, 90 lb. or otherwise as specified. 

No. 1. 5 min. on and 5 min. off repeated to the end of the 
test. 

No. 2. 7 min. on and 3 min. off repeated to the end of the 
test. 

No. 3. Continuously. 

Heat runs at other pressures and cycles of time operation 
should be made as specified for the given machine. 

The machine should be allowed to stand idle not less than 
eight hours between each test and in each case the test should be 
continued until either the temperatures of the armature and 
field become constant or until the temperature rise amounts to 
125 deg. cent, by resistance measurement. The commutator door 
and all covers should be kept closed during the test and unless 
otherwise specified, the machine should operate at 600 volts and 
pump against 90 lb. gauge pressure. Temperatures and resist- 
ances should be taken at regular intervals throughout the run, 
and final temperatures and resistances at the end. 

From the results of the test, curves should be drawn on one 
sheet, of the temperature rise by thermometer of the field coil 
against time as abscissae. Over these, curves of temperature 
rise by resistance measurement should be drawn. 

On another sheet a similar set of curves should be made for 
the armature. 

On the third sheet should be plotted a series of curves of 
thermometer rise at the end of each hour against the percentage 
of operating time. 

In connection with run No. 3 the compressor capacity should 
be taken as nearly cold as possible and at frequent intervals 
throughout the test. Temperatures should be taken every five 
minutes on the cylinder and exhaust chamber. The temperature 
rise of the cylinder and exhaust chambers, watthours per cu. ft. 
of free air, and cu. ft. of free air per minute should be plotted 
against time. The volume and temperature of the air in the 
measuring tank must be known to determine the watthours per 

316 



cu. ft. A curve should be plotted showing the relation of capac- 
ity to cylinder temperature. 

Starting Tests 

The starting tests for direct current air compressors should 
consist of tests made at various reduced voltages making note 
of the current, voltage and rev. per min. of the motor expressed 
on the testing record as r.p.m. of the compressor. The manner 
of starting of the compressor should be observed and noted, that 
is, whether it starts properly from rest or whether it hesitates 
and starts with an irregular rotation of the motor, or finally 
whether it fails to slart at all. 

In taking starting tests for alternating current motors 
special attention should be paid to the equipment serving the 
motors with current; that is, it should be sufficiently large so 
that the momentary conditions existing when the compressor 
is starting from rest against full load pressure do not cause any 
material drop in voltage. These tests should be repeated step 
by step at various voltages to determine the conditions under 
which the compressor starts irregularly, and finally fails to start. 

Oil Leakage Tests 

These tests commonly consist of a 20 hour half time cycle 
of compressor operation under the control of the governor. 
An oil separator is installed between the compressor and the 
tank for the purpose of taking these tests. After the com- 
pletion of the run the separator and tank should be allowed to 
stand at least an hour to allow the oil to collect at the draw off 
valves. It should then be drawn off, measured and the quantity 
noted, both separately as collected from the separator and the 
tank and the total quantity. Any water found in the graduated 
glass with which the measurement is made should be deducted. 



317 



CHAPTER 18 



VOLTAGE REGULATORS 

General Principle of Operation 

Voltage regulators are used to control the voltage of a 
circuit within narrow limits by rapidly opening and closing 
a shunt circuit connected across the field rheostat of the exciting 
circuit of the generator. Those for use for a-c. generators are 
known as Type TA, and those for use on d-c. circuits are Tvpe 
TD. 

TYPE TA REGULATORS 

TYPE TA FORM A2 

These regulators operate by rapidly opening and closing 
a shunt circuit connected across the exciter field rheostat. 
Actual electrical connections vary, but a schematic diagram is 
shown in Fig. 141. 



Ma/'r? Contacts 



Corpper7s<2t/ngr 



Current 
Transformer 




AC Fi eld. ^AC Generator 
ftheostat 
Fig. 141 
ELEMENTARY DIAGRAM OF TA, FORM A REGULATOR 

The regulator has a d-c. control magnet, an a-c. control 
magnet and a relay. The d-c. control magnet is connected to the 
exciter busbars and has a fixed stop core in the bottom and a 
movable core in the top which is attached to a pivoted lever 
having at the opposite end a flexible contact pulled downward 
by four spiral springs. The a-c. control magnet has a potential 
winding and also an adjustable compensating winding connected 
through a current transformer to the principal feeder. This 
compensating winding raises the voltage of the a-c. busbars 
as the load increases, and thus compensates for line drop. 
The a-c. control magnet has a movable core and a lever and 
contacts similar to those of the d-c. control magnet, and the 
two combined produce the "floating main contacts." The relay 
coil has a differential winding and a pivoted armature controlling 

318 



the contacts which open and close a shunt circuit across- the 
exciter field rheostat. One of the differential windings is per- 
manently connected across the exciter busbars and tends to 
keep the contacts open; the other is connected to the exciter 
busbars through the floating main contacts, and when the 
latter are closed, neutralizes the effect of the first winding and 
allows the relay contacts to short-circuit the exciter field rheostat. 
Condensers are connected across the contacts to prevent arcing 
and possible injury. 

CYCLE OF OPERATION 

The circuit shunting the exciter field rheostat through the 
relay contacts is opened by means of a single-pole switch at the 
bottom of the regulator panel and the rheostat turned in until 
the alternating voltage is reduced 65 per cent below normal. 




Fig. 142 

ELEMENTARY DIAGRAM OF TYPE TA, FORM F3 REGULATOR 

CONNECTIONS 

This weakens both of the control magnets and the floating main 
contacts are closed. This closes the relay circuit and demag- 
netizes the relay magnet, releasing the relay armature, and the 
spring closes the relay contacts. The single-pole switch is then 
closed and as the exciter field rheostat is short-circuited the 
exciter voltage will at once rise and bring up the voltage of the 
alternator. This will strengthen the alternating current and 
direct current control magnets and at the voltage for which 
the counterweight has been adjusted the main contacts will 
open. The relay magnet will then attract its armature and by 
opening the shunt circuit at the relay contacts will throw the full 
resistance into the exciter field circuit tending to lower the 
exciter and alternator voltage. The main contacts will then 

319 



again be closed, the exciter field rheostat short-circuited through 
the relay contacts and the cycle repeated. This operation is 
continued at a high rate of vibration due to the sensitiveness 
of the control magnets and maintains a steady exciter voltage. 

TYPE TA FORM F 

The TA Form F Regulator has several relays according to 
the size and number of exciters used. The principle of operation 
is the same as for the Form A2. An elementary diagram is 
given in Fig. 142. 

TYPE TD REGULATORS 

The Type TD Regulator consists essentially of a main control 
magnet with two independent windings, and a series wound relay 
magnet. The elementary connections are shown in Fig. 143. 

Comp ens a t mg 
Resistance Shunt 



^^M 



Sfide\ 



Potentia/ 
I Winding 



To Line I . — 

Compensating 
Winding 

Main Control 
Magnet- 




Generator 
maybe Shunt or 
compound wound 

\ 



fie/ay \ 

Contacts\ Condenser j» ( . 

^p g Generator Field 




ffe/ay 
Magnet 



rotor j 
Rheostat 



%Extema//teSistonce% 



Fig. 143 

DIAGRAM SHOWING ELEMENTARY CONNECTIONS OF 

TYPE TD REGULATOR 



The potential winding of the main control magnet is con- 
nected across the generator terminals, and the compensating 
winding across a shunt in one of the load mains, and opposes 
the action of the potential winding, so that as the load increases 
a higher potential at the generator is necessary to overcome the 
line drop. The control magnet has an adjustable stop core at 
the bottom with a movable core above. The movable core is 
attached to a lever operating the main contacts, the pull of the 
magnet being opposed by a spiral spring which tends to keep 
the main contacts closed. 

The armature of the relay magnet operates the contacts that 
open and close the shunt circuit across the field rheostat. The 
relay magnet winding is permanently connected, through resist- 
ance, to the busbars, and this winding is short-circuited by the 

320 



main contacts of the control magnet. When the main contacts 
are open the relay contacts are open. 

CYCLE OF OPERATION 

The shunt circuit across the generator field rheostat is first 
opened by means of a switch on the base of the regulator and the 
rheostat turned to a point that will reduce the generator voltage 
35 per cent below normal. The main control magnet is at once 
weakened and allows the spring to pull out the movable core 
until the main contacts are closed. This short circuits the relay 
winding, which demagnetizes the relay magnet core. The 
relay spring then lifts the armature and closes the relay con- 
tacts. The switch in the shunt circuit across the generator 
field rheostat is now closed, practically short-circuiting the field 
rheostat, and the generator voltage at once rises. As soon as it 
reaches the point for which the regulator has been adjusted the 
main control magnet causes its movable core to open the main 
contacts, which in turn open the relay contacts across the 
rheostat. The rheostat is thus connected in the field circuit, the 
voltage at once falls off, the main contacts are closed, the relay 
armature is released and the shunt circuit across the rheostat 
again completed. The voltage then starts to rise and this cycle 
of operation is continued at a high rate of vibration maintaining 
a steady voltage at the busbars. 

TYPE TD FORM G 

The Form G Regulator is designed to control the voltage of 
generators of small capacity, and is provided with both potential 
and compensating winding on the main control magnet. It may 
be connected to several small compound wound machines 
operating in parallel. It is then used on only one of the gener- 
ators at a time, the others being allowed to "trail" by means of 
their compound winding and equalizers. 

TYPE TD FORM R 

The Form R Regulator operates as the Form G, but contains 
two, three or four separate relays, and is designed to control 
the voltage of two or more generators operating in parallel. 

TYPE TD FORM L 

The Form L Regulator is designed for use with two or more 
separately excited d-c. generators and operates the same as the 
Type TA, Form A2 regulator described above. 

ADJUSTMENT 

Before setting any voltage regulator upon the testing table 
the following defects should be looked for: Improper stamping 
of name plate, wrong stamping of resistance box, loose coils, loose 
magnet frames, loose or inclined dashpot, bent switches and 
studs, wrong a-c. cores. - Check the air gap on the relay, the 

321 



friction of the relay armature, alignment of the relay contacts, 
relay numbering, loose screws, and loose terminals. See that 
different kinds of nuts and washers are not used on the same 
stud, that compensating switches on the a-c. regulators are not 
stamped for the wrong direction. Care should be taken to see 
that the regulator hangs true after it is installed, as any variation 
may cause trouble in operation. Each regulator should be 
wired according to its print and no testing should be done if 
the terminals are stamped incorrectly or if connectors are on 
the wrong studs. The internal connections on the regulator 
should be inspected for loose joints, improper connections, or 
poorly soldered terminals. After the regulator has been wired 
properly the cores should be made to hang in the center of the 
magnet spools and the levers should not fit too loosely nor too 
tightly. 

HIGH POTENTIAL 

High potential should be applied to all parts of the regulator 
to ground and between coils. The potential between coils should 
not be instantaneously applied nor must the circuit be suddenly 
broken but the high potential terminals should be placed on the 
coil under test and the voltage gradually raised on the alternator 
to the desired amount and then reduced in the same manner 
until zero voltage is reached before removing the high potential 
leads. 

RESISTANCE MEASUREMENTS 

All relay coils, d-c. magnets, a-c. magnets and resistance 
boxes should have their resistance measurements carefully 
taken and the variations should not exceed those specified in the 
Engineering Brief which will be found in the files of the Testing 
Section. 

HEAT RUNS 

Heat runs are made on all regulators to determine the maxi- 
mum heating on the different coils and the external resistance. 
The run on the a-c. regulator is made at 115 volts, and at normal 
rated voltage on the d-c. coil. The run on the d-c. regulator is 
made at the standard rated voltage, the value of which will be 
found on the name plate of each regulator. The length of run 
in each case is three hours. 



ADJUSTMENT OF RELAY CONTACTS 

The manner of adjusting the relay contacts is the same on 
all regulators. Press the armature firmly against its stop 
stud and set the contacts, one directly over the other and ^ in. 
apart. 

322 



TYPE TA FORM A2 REGULATOR 

This type of regulator is built for the following standard 
voltages : 




Fig. 144 

DASHPOT FOR TYPES TA-60 AND TA-125, FORM A2 VOLTAGE 

REGULATOR FOR GENERATORS 



Type 



Form 



Exciter 
Volts 



Range of 
Exciter 
Volts 



A-C. Volts 



TA-60 

TA-90 

TA-125 

TA-250 

TA-550 



A2 
A2 
A2 
A2 
A2 



90 
125 

250 
550 



33/67 

50/100 

70/140 

140/280 

308/616 



100 to 125 
100 to 125 
100 to 125 
100 to 125 
100 to 125 



ADJUSTMENT OF DASHPOT 

The dashpot is shown in section in Fig. 144. The piston fits 
closely, but should move freely, as friction will result in unstable 
voltage. The piston (1) is attached to the lower end of the 
alternating current magnet core stem (2) and its normal position 
is about midway between the two port holes (3) and (4). Piston 

323 



(5) may be raised by turning thumbscrew (6). This results in 
closing port hole (4) thus retarding the movement of piston (1). 
When the port hole is entirely closed and the dashpot full of oil, 
the piston moves very slowly. The dashpot should never be filled 
with anything but light dynamo oil. This can best be done as 
follows : 

Remove screws (10) and (11), give the dashpot a quarter 
turn, then it can readily be taken off. See that it is free from all 
dirt, then fill it to within about z /% in. of the top, replace it and 
securely tighten screws (10) and (11); the oil should then stand 




Fig. 145 

MAIN CONTROL MAGNETS AND LEVERS FOR TYPES TA-60 

AND TA-125 FORM A2 VOLTAGE REGULATORS 

FOR GENERATORS 

about }/$ in. from the top of the cup. By raising and lowering 
core (8) by hand and at the same time varying the height of 
thumbscrew (6), the position of piston (5) can be readily deter- 
mined, as a slight change in the height of piston (5), when at the 
position shown varies greatly the free action of core (8). The 
dashpot should be adjusted until core (8) moves with very little 
retarding. The retarding effect of the dashpot necessarily 
depends entirely upon the time constants of the exciters and 
generators but ordinarily the piston should move freely. 

ADJUSTMENT OF SPRINGS NOS. 1, 2, 3 AND 4 FOR 
TA-125 REGULATORS 
Before adjusting lever (5) Fig. 145, core (11) should be raised 
to its highest position and blocked, thus bringing main contact 

324 



(30) to its lowest position, to prevent contact being made be- 
tween (19) and (30) while lever (5) is being adjusted. This is 
necessary since if contacts (19) and (30) were to come together, 
the proper adjustment of lever (5) could not be made. Springs 
(1), (2) and (3) should be loosened to their extent or taken out 
while spring (4) is being adjusted. A gauge for use in adjusting 
lever (5) is always furnished with the regulator. To adjust 
spring (4) first see that the voltage on the exciter to which the 
direct current control magnet (6) is connected, is maintained 
at 65 volts. Then by taking the gauge between the thumb and 
index finger at "A" place it firmly against the brackets "B" and 
"C" and against the under side of pivot sockets (7) and (8) as 
illustrated. Then adjust spring (4) by means of the small nut 
at the top of its adjusting screw, until the under side of lever 
(5) comes even with the top of the gauge at (9). After this 
adjustment has been made, the exciter voltage should be 
increased to 122, and at exactly this point spring (4) should be 
overpowered by the magnet, and the cores (12) and (13) will 
come together. Should it require more or less voltage to over- 
power the spring and bring these cores together, core (13) 
should be either raised or lowered, and spring (4) readjusted 
until the under side of lever (5) comes to the gauge as before. 
The adjustment of spring (4), lever (5), and core (13) must be 
repeated several times to insure correctness as this adjustment is 
of the utmost importance. After the proper adjustment has been 
obtained, the lock nut beneath the lever on spring (4) should be 
securely tightened after which the exciter voltage should again 
be varied over its range, and the adjustments checked. 
Then screw (14), which holds stop core (13) in position, should 
be securely tightened. This screw should, however, be kept well 
tightened while the adjustments are being made. After these 
adjustments have been made, spring (1) should be adjusted by 
raising the exciter voltage to 90, and at exactly this point this 
spring should begin to come under tension, and the small head 
(15) on the spring stem will be brought in contact with the spring 
support (16). After this adjustment has been carefully made, 
the lock nut below the lever on spring (1) should be securely 
tightened and the adjustment of spring (1) checked to see if 
it is correct. Then spring (2) should be adjusted by increasing 
the exciter voltage to 115, when it will come into action as does 
spring (1). After adjusting this spring, the lock nut beneath the 
lever on spring (2) should also be securely tightened and the 
adjustment checked. Spring (3) should then be adjusted by 
raising the exciter voltage to 138, at which point this spring will 
come into action as did springs (1) and (2). Following this 
adjustment, the lock nut underneath the lever on spring (3) 
should be securely tightened and the adjustment of spring (3) 
checked. 

Springs for Standard Regulators are adjusted as in the fol- 
lowing table: 



325 



TYPE TA-60 VOLTAGE REGULATORS 

Spring No. 4 adjusted with gauge at 31 volts. 
Spring No. 1 adjusted to pick up at 43 volts. 
Spring No. 2 adjusted to pick up at 55 volts. 
Spring No. 3 adjusted to pick up at 66 volts. 

TYPE TA-90 VOLTAGE REGULATORS 

Spring No. 4 adjusted with gauge at 47 volts. 
Spring No. 1 adjusted to pick up at 65 volts. 
Spring No. 2 adjusted to pick up at 83 volts. 
Spring No. 3 adjusted to pick up at 99 volts. 

TYPE TA-125 VOLTAGE REGULATORS 

Spring No. 4 adjusted with gauge at 65 volts. 
Spring No. 1 adjusted to pick up at 90 volts. 
Spring No. 2 adjusted to pick up at 115 volts. 
Spring No. 3 adjusted to pick up at 138 volts. 

TYPE TA-250 VOLTAGE REGULATORS 

Spring No. 4 adjusted with gauge at 130 volts. 
Spring No. 1 adjusted to pick up at 180 volts. 
Spring No. 2 adjusted to pick up at 230 volts. 
Spring No. 3 adjusted to pick up at 275 volts. 

TYPE TA-550 VOLTAGE REGULATORS 

Spring No. 4 adjusted with gauge at 286 volts. 
Spring No. 1 adjusted to pick up at 396 volts. 
Spring No. 2 adjusted to pick up at 506 volts. 
Spring No. 3 adjusted to pick up at 607 volts. 

ADJUSTMENT OF THE FLOATING MAIN CONTACTS 

Main contacts (19) and (30) are specially constructed, and no 
contacts other than those supplied by the General Electric 
Company should be used. Care should be taken in grinding 
them not to cut away any more of the metal than is necessary. 

For the proper adjustment of these points, maintain 65 volts 
on the exciter and with levers (5) and (17) in position according 
to gauge, the contacts should be set squarely one above the 
other after which screws (31) and (32) should be securely tight- 
ened. 

With levers (5) and (17) in this position, the upper contact 
(19) should be raised or lowered until it will just touch contact 
(30), after which the set screw (20) should be securely tightened. 
Screw (21) should be adjusted to within ^ in. of screw (19) 
and lock nut (22) securely tightened. With lever (17) still in its 
proper position, screw (33) should be adjusted to within ^ in. 
of lever (17) and nut (34) securely tightened. 

The screw (33) is for the purpose of limiting the excessive 
upward travel of lever (17) ; and immediately back of this screw, 
passing through the same post is a threaded stud extending down 

326 



and bent at right angles to extend underneath lever (17). This 
stud should be so adjusted as to limit the downward travel of 
lever (17) at 20 per cent above normal exciter voltage or 150 volts 
on a 125 volt exciter. 

ADJUSTMENT OF THE A-C. MAGNET CORE 

If the alternator voltage varies through the range of exciter 
voltage as specified, it would indicate an improper adjustment 
of the a-c. magnet core (11) and to correct this, proceed in the 
following manner: 

The exciter voltage should be varied from 70 to 140 volts by 
means of the a-c. generator field rheostat, and if the alternating 
voltage rises or falls, core (11) should be raised or lowered on 
stem (24) until at a point that will give neither rise nor fall in 
the alternating voltage on varying the exciter voltage from 70 
to 140. If the alternating voltage falls on increasing the exciter 
voltage from 70 to 140, core (11) should be lowered or vice versa. 
After this adjustment has been determined, lock nuts (26) and 
(27) should be securely tightened, and the previous adjustment 
checked. 

The values given for the adjustment of the a-c. magnet core 
(11) of 70 volts to 140 volts are for 125 volt regulators and 
exciters. Other standard regulator and exciter voltages are as 
follows: 



Minimum 


Normal Standard 


Maximum 


Excitation Voltage 


Exciter Voltage 


Exciter Voltage 


33 


60 


«7 

6/ 


50 


90 


100 


70 


125 


140 


140 


250 


280 


308 


550 


616 



For the proper adjustment of core (11) see also "Error in 
Voltage" under the heading "Locating Trouble" on page 332. 

ADJUSTMENT OF RELAY 

A complete side view showing the connections of the relay, 
etc., is shown in Fig. 146. As this relay is differentially wound 
with two windings on each spool, there are four leads extending 
from the side of each magnet spool. The two outer terminals 
represent one winding and the other corresponding two inner 
leads are connected to the other winding. These leads are 
connected to binding posts A, B and C as follows: 

(3) and (5) to "A." 

(2), (4), (6) and (8) to "B." 

(1) and (7) to "C." 

Xo two of the various holes in the three binding posts are at 
the same distance from the panel, and each lead from the spools 

327 



is brought out opposite the binding post hole in which it should 
be inserted, thus rendering the connections very simple. Inas- 
much as the relays are differentially wound, they will work to 
some extent whether the windings are in service or not. There- 
fore, if the relays operate unsatisfactorily they should be tested 
to ascertain whether the coils are all working properly. Should 
trouble be experienced which is apparently due to improper 
connection of the relay magnets or a possible open circuit, the 



iOw — 




EGaZter" ^^Ca^S^ i 



2 



33 



a 



<?e 



WQ, 



fcsc 



^n 



LrA- 



y 



^^ 



Fig. 146 

RELAY FOR TYPES TA-60 AND TA-125 FORM A2 VOLTAGE 

REGULATOR FOR GENERATORS 

fault may be easily located by ringing out the different coils 
with a magneto or other circuit-testing device; when this is 
done all leads should be disconnected from their respective bind- 
ing posts. It is also important to ascertain that all the leads 
are properly connected to posts (A), (B) and (C) and that the 
set screws holding them are securely tightened. See that the 
expanded core tips (11) and (12) are flush with the ends of the 
wire cores; then securely tighten set screws (22) and (23). 

Pivot holder (16) should be adjusted on the pivot until 
contact stud (17) clears stop stud (14) by j$ in. The set screws 
holding the pivot sockets should be tightly secured, leaving no 
end play in the pivots. 

328 



With contact holder (13) resting upon stop stud (14), core tips 
(11) and (12) should be only ^ in. from armature (9). This 
distance is very important and should be measured by gauge. 
After these have been adjusted the four set screws on the 
opposite side of the spools holding the iron cores in position 
should be securely tightened. 

Setting of Relay Adjusting Springs 

With the relay contacts (18) and (19), Fig. 146, properly 
adjusted (see adjustment of relay contacts, page 322) and 
insulating material placed between the floating main contacts 
(19) and (30), Fig. 145, the relay armature should be so adjusted 
by means of spring (10), Fig. 146, that with 45 volts on the exciter, 
the contact (19) just floats midway between the upper relay 
contact (18) and the stop stud (14). 

After the movable relay contact which is attached to the 
armature has been adjusted in accordance with the above 
instructions, the lock nut (21) should be securely tightened. 

The above value of 45 volts applies to 125 volt exciters and 
for the other standard voltages this adjustment figure is directly 
proportional, as is indicated by the following table: 





Values for Relav 


Exciter Volts 


Spring Adjustments 


60 


22 


90 


32 


125 


45 


250 


90 


550 


197 



CONNECTIONS FOR LINE DROP COMPENSATION 

The compensation may be accomplished by a single current 
transformer which has its secondary connected to an adjustable 
compensating winding on the a-c. control magnet as shown in the 
standard diagrams. This transformer is preferably connected to 
the main feeders and care should be taken that it be inserted in 
one of the mains to which the potential transformer is connected; 
for with three-phase as well as with two-phase currents, if the 
current transformer is not connected to one of the same leads 
with the potential transformer it is obvious that at unity power- 
factor the current in the potential winding will be displaced by 
an angle of 90 deg. from that in the current winding; therefore, 
no compensating effect whatever will be obtained, although in 
cases where the power-factor is below unity there would be a 
slight compensation due to the lagging current. 

In all cases, the current transformer should be placed beyond 
the point where any load is taken off at the station, such as 
motor load, constant current transformers, etc., as the draught 

329 



of current through the current transformer for such loads would 
increase the busbar voltage as though the load were out on the 
line, which would be undesirable. A current transformer that 
will give 33^ amperes secondary will compensate for about 15 
per cent line drop. 




Fig. 147 

CONNECTIONS OF POTENTIAL AND COMPENSATING WINDING 

OF TYPES TA-60 AND TA-125 FORM A2 VOLTAGE 

REGULATORS FOR GENERATORS 



The compensating winding (see Fig. 147) consists of three 
layers of wire, the two inner layers of which are connected as 
follows: The terminals of the first winding are connected to 
buttons (1) and (2) while the second winding is connected to but- 
tons (2) and (3). The third layer is divided into sections of 
(5) turns each, which have taps brought out to buttons (4) to 
(11) inclusive. Over these buttons, levers (A) and (B) are 
arranged to swing. 

In order to increase the busbar voltage the current in these 
windings should oppose the current in the potential winding. 

330 



Therefore, if it is found that with a load on the generator and the 
levers (A) and (B) swung to the right, the busbar voltage falls, 
it would indicate that the current in the compensating windings 
is assisting the current in the potential windings in which case 
the leads from the secondary of the current transformer to the 
regulator should be reversed. 

LOCATING TROUBLE 

Should the regulator fail to build up the voltage 

(1) See that the reversing switches at the bottom of the 
regulator base are thrown to the extreme position either up or 
down. 

(2) See if the single pole switches at the bottom of the 
regulator base are closed on the proper exciters. 

(3) Look for improper connections. 

Should the voltage fall 

Examine the rheostat shunt circuit connections to see if 
they are not so connected as to short-circuit the exciter field 
instead of its field rheostat. 

Fluctuating Voltage 

If, after placing the regulator in service the potential fluctu- 
ates to the extent of several volts, proceed as follows: 

First — See that screw (21), Fig. 145, is properly adjusted as 
contact between screws (19) and (21) will cause unsteady voltage 
to the extent of from 5 to 10 volts on the secondary. (See 
"Adjustment of Main Contacts," page 326.) 

Second — See if contact screw (19) is loose. If so it should be 
properly adjusted and set screw (20) securely tightened. 

Third — Observe both levers (5) and (17) at the points where 
the core stems (23) and (24) are attached, to see that there is no 
friction at these points. 

Fourth — The regulator should not be subjected to excessive 
vibration such as might be the case when it is mounted on iron 
brackets. Should such vibration exist, some rigid support 
should be provided to overcome it. 

Fifth — The dashpot should be carefully inspected to see that 
it is actually full of oil within ^g i n - of the top. 

Sixth — The dashpot should be examined to see that it is 
securely attached to the supporting posts. 

Seventh — The dashpot may be adjusted for too free a move- 
ment. This adjustment should be made as free as possible 
without causing "pumping" of the voltage at no load. (See 
"Adjustment of Dashpot," page 323.) 

Eighth — Examine cores (11) and (12) to see that they do not 
touch the inside of the magnet spools. 

Ninth — Carefully inspect all wiring, looking for such mistakes 
as using the same lead for binding posts (1) and (14) (on standard 
diagrams filed in the section), flat spots on the exciter commu- 
tators, loose brushes, or any other poor contacts that might 
cause an unsteady voltage. 

331 



Tenth — Observe pin (35), Fig. 145, to see that it does not make 
contact with spring (29), and that set screw (36) is securely- 
tightened. 

Error in Voltage 

If there is an error in voltage from no load to full load without 
the compensating winding in circuit, it must be due to improper 
adjustment of the alternating current magnet core. 

If after the core has become steady in going from no load 
to full load, the main alternating voltage has fallen off, it would 
indicate that the a-c. magnet core should be lowered slightly 
until the voltage is the same at full load as at no load. If on the 
other hand, the main alternating voltage is too high, it would 
indicate that the a-c. core should be raised slightly to overcome 
the error. 

With ordinary exciters, if the a-c. magnet core is adjusted 
while the lever is in a horizontal position so that the core extends 
from the bottom of the spool to the end of the cap 1% in. there 
is usually no error from no load to full load on the a-c. generators 
or with the exciter voltage varied from 70 to 140 volts. (For 
further adjustments see " Adjustment of the A-C. Magnet Core. ' ') 

If this adjustment is checked and found correct, the error 
may be caused by friction in the core stems on the magnet levers. 

Error Due to Compensating Winding 

If there is an error in voltage when using the compensating 
winding, such as too high voltage at no load and corresponding 
low voltage at full load at the center of distribution, thus requir- 
ing daily adjustment of levers (A) and (B) (see Fig. 147), it would 
indicate that the ratio of levers (A) and (B) is incorrect and that 
they should be swung further to the right and the alternating 
voltage lowered by means of counterweight (25) and spring 
(29). See Fig. 145. After the setting of these levers is once 
obtained, they should require no further adjustment, as it is 
evident that they will automatically compensate for voltage at 
all loads. (See "Connections for Line Drop Compensation," 
page 329.) 

Arcing at the Relay Contacts 

If there is excessive arcing at the relay contacts: 
First — Check the connections of the rheostat shunt circuit 
to binding posts (7), (8), (12), (13) and (14) on standard diagrams 
to see that they are properly made, and that the rheostat only 
is being short-circuited. Also see that separate leads are run 
from the exciter busses to binding posts (1) and (14) on the 
regulator. 

Second — The connections of the condensers should be 
checked. 

CONDENSERS 

The condensers furnished with the regulator should be con- 
nected in multiple if more than one is required, and connected 

332 



to binding posts (6) and (11) (on standard diagrams). The 
number of condensers required should, roughly speaking, be one 
section for each 15 kw. or fraction thereof for exciters having 
laminated poles, and for each 22 kw. for exciters having solid 
poles. 

TA FORM "L" REGULATORS 

The Form L voltage regulator is the same as the A2 with the 
exception that it is for mounting directly upon the switchboard 
panel while the Form A2 regulator is mounted upon its own base. 
The instructions given for the Form A2 also apply for the 
Form L. 

TA FORM "F" REGULATORS 

The Type TA Form F regulators have the following standard 
voltages. 



Type 


Form 


Exciter 
Volts 


Range of 
Exciter Volts 


Alternating 
Voltage 


TA-90 

TA-125 

TA-250 


F 

F 
F 


90 
125 
250 


50/100 

70/140 
140/280 


100 to 125 
100 to 125 
100 to 125 



ADJUSTMENT OF DASHPOT 

See instructions under Form A2 regulators. 



ADJUSTMENT OF LEVERS AND SPRINGS 

Levers 

First — See that the center of the slot in which core stems 

(23) and (24), Fig. 148, are attached to the levers, is 1& inch from 
the marble base. After the levers and pivots have been set to 
give this distance, see that the set screws securing the levers to 
the pivots, and those holding the pivot sockets, are securely 
tightened. The pivots should be adjusted until they have but a 
slight amount of end play. Be sure that the core stems (23) and 

(24) do not bind in the slots in the levers; they should always 
have sufficient clearance to prevent binding, as friction at this 
point would be a serious defect. 

Springs 

Before adjusting lever (5) core (11) should be raised to its 
highest position and blocked by some means, thus bringing 
main contact (30) to its lowest possible position, to prevent 
contact being made between contacts (19) and (30) while 
adjusting lever (5). Springs (1), (2) and (3) should be loosened 
to their full extent, or taken out while spring (4) is being adjusted. 

333 



To adjust spring (4), first see that the voltage on the exciter, to 
which the direct current control magnet (6) is connected, is 
maintained at 60, assuming that a 125 volt regulator is being 
adjusted. Then adjust spring (4) by means of the small nut at 
the top of its adjusting screw, until the under side of lever (5) 
comes even with the white mark on gauge (37). After this 
adjustment has been made the exciter voltage should be increased 
to 112 and at exactly this point, spring (4) should be over- 
powered by the magnet, and the cores (12) and (13) will come 
together. Should it require more or less voltage to overpower 



se as 2a 




Fig. 148 
TYPE TA, FORM F VOLTAGE REGULATOR 
MAIN CONTROL MAGNETS AND LEVERS 



the spring and bring these cores together, core (13) should be 
either raised or lowered, and spring (4) readjusted until the 
under side of lever (5) comes to the gauge as before. The adjust- 
ment of spring (4), lever (5) and core (13) must be repeated 
several times to insure their being correct, as they are of the 
utmost importance. After the proper adjustment has been 
obtained, the lock nut beneath the lever on spring (4) should be 
securely tightened, after which the exciter voltage should be 
varied over its range again, and the adjustments checked. 
Then screw (14) which holds the stop core (13) in position, 
should be securely tightened. This screw should, however, be 
kept well tightened while the above adjustments are being made. 
Spring (1) should be adjusted by raising the exciter voltage to 
80 and at exactly this point this spring should begin to come 

334 



under tension, and the small head (15) on the spring stem will 
be brought in contact with the spring support (16). After this 
adjustment has been carefully made the lock nut below the lever 
on springi(l) should be securely tightened and the adjustment 
of spring (1) checked to see if it is correct. Then spring (2) 
should be adjusted by increasing the exciter voltage to 110, 
when it will come into action as does spring (1). After adjusting 
this spring, the lock nut beneath the lever on spring (2) should 
also be securely tightened and the adjustment checked. Spring 
(3) should then be adjusted by raising the exciter voltage to 
123 at which point this spring will come into action as did 
springs (1) and (2). Following this adjustment the lock nut 
underneath the lever on spring (3) should be securely tightened 
and the adjustment of spring (3) checked. The values of the 
different adjustment voltages in accordance with the standard 
exciter voltages for which the regulators are designed are 
tabulated as follows: 

TYPE TA-60 VOLTAGE REGULATORS 

Spring No. 4 adjusted to gauge mark at 29 volts. 
Spring Xo. 1 adjusted to pick up at 38 volts. 
Spring Xo. 2 adjusted to pick up at 53 volts. 
Spring Xo. 3 adjusted to pick up at 59 volts. 

TYPE TA-90 VOLTAGE REGULATORS 

Spring Xo. 4 adjusted to gauge mark at 43 volts. 
Spring Xo. 1 adjusted to pick up at 58 volts. 
Spring Xo. 2 adjusted to pick up at 79 volts. 
Spring Xo. 3 adjusted to pick up at 89 volts. 

TYPE TA-125 VOLTAGE REGULATORS 

Spring Xo. 4 adjusted to gauge mark at 60 volts. 
Spring Xo. 1 adjusted to pick up at 80 volts. 
Spring Xo. 2 adjusted to pick up at 110 volts. 
Spring Xo. 3 adjusted to pick up at 123 volts. 

TYPE TA-250 VOLTAGE REGULATORS 

Spring Xo. 4 adjusted to gauge mark at 120 volts. 
Spring Xo. 1 adjusted to pick up at 160 volts. 
Spring Xo. 2 adjusted to pick up at 220 volts. 
Spring Xo. 3 adjusted to pick up at 246 volts. 

TYPE TA-550 VOLTAGE REGULATORS 

Spring Xo. 4 adjusted to gauge mark at 264 volts. 
Spring Xo. 1 adjusted to pick up at 352 volts. 
Spring Xo. 2 adjusted to pick up at 484 volts. 
Spring Xo. 3 adjusted to pick up at 541 volts. 

335 




Fig. 149 

SECTION OF RELAY MAGNET FOR TYPE TA FORM F 

VOLTAGE REGULATOR 



1 


Connection strip 


14 1 Adjustment screws for 


2 


Armature 


15 j 


spring contact 


3 


Pivot bearing 


16 


Spring contact 


4 


Relay armature lever 


17 


Contact in armature head 


,T 




18 


Armature head 


6 


► Set screws 


19 


Relay spring for adjust- 


7 






ment screw 


8 




20 


Core plate 


9 


[ Expanded core tips 


21 


Adjustment spring 


10 




22 


Set screw 


11 


Stop stud for spring relay 


23 


Lock nut 




contacts 


24 


Adjusting nut 


12 


1 Set screws for spring 


25 


Contact stud 


13 


J contact 







336 



ADJUSTMENT OF THE FLOATING MAIN CONTACTS 

For the proper adjustment of the main contacts (19) and 
(30) swing block (37) underneath lever (5) and tighten screw (39) 
then swing block (38) underneath lever (17), and with levers 
(5) and (17) both resting upon blocks (37) and (38), first, see 
that contact screw (30) is securely tightened and that the con- 
tact screw (19) is centrally placed above contact screw (30), then 
securely tighten screws (31) and (32), after which contact screw 

(19) should be adjusted to just touch contact (30) and set-screw 

(20) securely tightened. Then blocks (37) and (38) should be 
swung out from under levers (5) and (17) so that engagement 
with them is impossible, and they should be securely tightened 
in this position. 

ADJUSTMENT OF THE A-C. MAGNET CORE 

If the alternating voltage varies through the regulator range 
of exciter voltage as specified, it indicates an improper adjust- 
ment of the alternating current magnet core and to correct this 
error, proceed as for the Form A2 regulator. 

ADJUSTMENT OF RELAY 

A complete sectional side view of the relay is shown in Fig. 149. 
As this relay is differentially wound with two windings in each 
coil, there are four leads extending from the side of each coil. 
These leads (not shown in Fig. 149) are connected to binding 
posts A, B and C (on the regulator base) in the following manner: 

1 and 6 to "A." 

2, 3, 5 and 8 to "B." 

4 and 7 to "C." 

The above leads are all provided with stamped metal tags, 
thus rendering their connection very simple, which should 
therefore obviate any possibility of a mistake. Inasmuch as the 
relays are differentially wound, they will work to some extent 
whether the windings are in service or not. Therefore, if the 
relays operate unsatisfactorily, they should be tested to ascertain 
whether the coils are all working properly. If trouble is expe- 
rienced which is apparently due to improper connections of the 
relay magnets or a possible open circuit, the fault may be easily 
located by ringing out the different coils with a magneto or other 
circuit-testing device. Each coil is wound with two well insu- 
lated parallel conductors, therefore, when testing the coils care 
should be taken to see that there is no breakdown of insulation 
between the two windings. It is also important to ascertain 
that all leads are properly connected to posts A, B and C, and 
that the set screws holding them are securely tightened. See 
that the expanded core tips (8), (9) and (10) (Fig. 149) are flush 
with the ends of the cores; then securely tighten set screws 
(5), (6) and (7). 

The pivot holder on the end of armature (2) should be adjusted 
on the pivot until armature (2) stands centrally over the core 
tips (8), (9) and (10). The set screws holding pivot and sockets 

337 



should then be securely tightened, leaving no end play in the 
pivots. 

With armature (2) resting upon stop cap (10), the core and 
tips (8) and (9) should be only 0.05 in. from armature (2). This 
distance is very important and should be measured by gauge. 

Setting of Relay Adjusting Spring 

With the relay contacts (16) and (17) properly adjusted (see 
"Adjustment of Relay Contacts") and insulating material 
placed between the floating main contacts (19) and (30) (Fig. 
148) the relay armature should be so adjusted by means of 
spring (21) that with 45 volts on the exciter the armature (2) 
just floats midway between the upper relay contact (16) and 
the stop cap (10). 

The above value of 45 volts applies to 125 volt exciters and 
for the other standard voltages this adjustment figure is directly 
proportional, as indicated by the table below: 



Exciter Volts 


Values for Relay- 
Spring Adjustments 


60 


22 


90 


32 


125 


45 


250 


90 


550 


197 



LOCATING TROUBLE 

See instructions under the Form A2 regulators. 

CONDENSERS 

With each regulator there should be furnished one con- 
denser section for each pair of relay contacts. 

TA FORM K REGULATORS 

There is the same difference between the Forms F and K 
as there is between the A2 and the L, that is, the Form F is 
mounted upon its own base while the Form K has the regulator 
parts mounted directly upon the switchboard panel. The same 
instructions given for the Form F also apply for the Form K. 

TYPE TD FORM G VOLTAGE REGULATORS 

ADJUSTMENT OF MAIN CONTROL MAGNET 

Should the voltage be unstable or fluctuating, the adjust- 
ments of the main control magnet should be gone over as follows: 
With normal voltage on the generator, contacts (4) and (5) (Fig. 
150) will be nearly closed and the lever (6) should be in a horizon- 

338 






tal position. Then with an increase in voltage of 12 per cent, 
core (9) should jump back and strike core (10). Should this 
fail to occur at 12 per cent above normal voltage, core (10) 
should be turned in one direction or the other and spring (8) 
should be adjusted until the lever is again in a horizontal position. 
The voltage should then again be raised to 12 per cent above 
normal. The adjustment of these cores is very important and 




Fig. 150 

MAIN CONTROL MAGNET FOR TYPE TD, FORMS G AND R 

VOLTAGE REGULATOR FOR DIRECT CURRENT 

GENERATORS 



should be checked carefully. Make sure that pivots (15) are 
free and do not stick. A drop of oil on these pivots occasionally 
will prevent their rusting. 

ADJUSTMENT OF RELAY MAGNET 

The adjustment of the relay magnet is not the same on all 
TD regulators. A side view of the Forms S and G relay is shown 
in Fig. 151. The easiest way to adjust the relay contacts is to bring 
the voltage on 125 volt regulators to 88 volts or 30 per cent below 
normal. At this voltage the contacts should not open or close 
but should just come to a balance. If these contacts are open 
at this voltage lock nut (12) should be loosened and spring (10) 
should be tightened until the contacts merely come to a balance, 
then lock nut (12) should be securely tightened. In adjusting 

339 



the relay magnet, before attempting to adjust the contacts the 
relay cores (3) and (4) should be t& in. from the armature with 
the armature resting on stop stud (6). 

TYPE TD FORM S REGULATORS 

The only difference between the Form G and the Form S 
regulator is that the latter has no compound winding. The 
adjustments are the same as for the Form G regulator. 




Fig. 151 

RELAY MAGNET FOR TYPE TD, FORMS G AND S VOLTAGE 

REGULATOR FOR DIRECT CURRENT GENERATORS 



TYPE TD FORM L REGULATORS 

The Type TD Form L regulator is an exact duplicate of the 
Type TA Form A2 regulator with the exception that the TD 
Form L is intended for a direct current generator separately 
excited by an exciter, while the Form A2 is for an a-c. generator 
separately excited from an exciter and therefore the instructions 
for the TA-A2 apply for the TD Form L regulator. 

TYPE TD FORM T REGULATORS 

The TD Form T regulator is the same as the TD Form L 
with the exception that the former is intended for mounting 
directly upon the switchboard panel while the latter is mounted 
directly upon its own base. The instructions given for the TA 
Form A2 also apply for the TD Form T regulators. 

340 



TYPE TD FORM R REGULATORS 
ADJUSTMENT OF MAIN CONTROL MAGNET 
See instructions for Type TD Form G regulators. 

ADJUSTMENT OF RELAY MAGNET 

Fig. 152 shows the side view of the relay magnet of the Form 
R regulator. This relay is differentially wound with parallel 
conductors having four windings on the two coils. Two windings 
are connected permanently in multiple to the busbar through an 
external resistance. The second two windings which are con- 
nected in multiple are opened and closed by the main contacts. 



uTTy—. — . 



/5 /6 9 dJ-i 




^^c-B^g^ 




Fig. 152 

RELAY FOR TYPE TD, FORM R VOLTAGE REGULATOR 

FOR DIRECT CURRENT GENERATORS 



The adjustment of this relay is exactly the same as that 
given under the adjustment of relay for the Type TA Form A2 
regulator with the exception of the spring setting. The tension 
of spring (10), Fig. 152, should be such that when the main con- 
tacts on the regulator are opened the relay armature (9) will 
just float midway between stop stud (14) and contact (18) with 
88 volts impressed on the generator. This value, 88, is for the 
125 volt regulator; for the 250 volt regulator this setting should 
be made at 176 volts. 

341 



The switch on the back of the relay is used for cutting out 
the relays which are not always in use and by opening this switch 
the main contacts have less work to do and consequently will 
last considerably longer. 

TYPE TD FORM W SPEED REGULATOR 

This regulator is intended to control the speed of d-c. motors 
and the adjusting spring (see Fig. 153) should be so adjusted 



Raise Speed By 
Increasing Tension 
on Spring \ 



Arrow Shows 
Direction of 
Rotation 




Contact Screw A 
an<^ Stop Screw 
° Interchanges 



g4 Clearance 
Bet ween 
Contacts with 
Motor 
Stationary 



For Clockwise Rotation 

r~/yyve/aht C Should 

Be Assembled in 

Dotted Position with 

Contact Screw A and 

"top Screw B Inter channel 



Brushes Should Bear 
Evenly on Collector 
Ririas Without Interference 
Due to End Play 



Fig. 153 

ADJUSTMENT OF SPEED CONTROLLER FOR 

DIRECT CURRENT MOTORS 



that the vibrating contacts just close at the desired speed. The 
regulating spring upon the back of this control device should be 
so adjusted that the contacts which this spring controls should 
open at about 15 to 20 per cent below normal speed. 

The function of these contacts is to short-circuit the motor 
field rheostat in starting to prevent the motor starting with a 
weak field. 

When relay magnets are furnished with this regulator their 
adjustment should be the same as that given under TD Form R 
regulators. 

342 



CHAPTER 19 

INDUSTRIAL CONTROL APPARATUS 

GENERAL 

Under this heading are included resistances, field, starting 
and regulating rheostats, and controllers. The Testing Dept. 
is responsible for detecting all mechanical and electrical defects 
on apparatus which passes through the Department. A me- 
chanical inspection should be given each piece of apparatus 
before the electrical test is begun. Particular care should be 
used in handling apparatus. Sliding contacts should move 
freely, contact brushes should make good contact on the seg- 
ments and have a uniform pressure throughout the arc of 
movement. See that no loose bolts, nuts, terminals, or name- 
plates are passed. Where bead insulation is employed, the 
leads should be provided with a sufficient number of beads to 
prevent a short-circuit in case two leads should touch one 
another. Terminals should be spaced a sufficient distance 
apart to insure safety for the voltage employed and should be 
stamped according to the DS sketch or drawing list, as the case 
may be. Xo apparatus except supply parts should be sent out 
without a nameplate stamped with the drawing list or catalogue 
number and rating of the apparatus, which will be given on the 
Engineering Notice, drawing list, or DS sketch. 

Owing to the fact that the resistance of materials is subject 
to considerable variation, a standard list of the allowances 
which are approved by the Engineering Dept. is posted in the 
Section. Devices whose resistance measures above or below 
these allowable percentages of variation from the specification 
should be rejected. All rheostats which have reversed, open, 
or short-circuited steps should be returned to the manufacturing 
department for repairs. The tester must assure himself, before 
approving any pieces of apparatus, that all circuits are wired 
according to the wiring diagrams. 

After all tests are complete, the nameplate should be marked 
by the tester to indicate that the test is complete, and the 
wiring sketch should be securely fastened to the apparatus 
for delivery to the Shipping Dept. 

Field Rheostats 

All field rheostats should receive an insulation test, as given 
in the Engineering Brief, and the total resistance and the 
resistance of each step should be read and checked up with 
the specifications, which will be called for on the drawing list. 
Hand operated or chain operated rheostats should have the 
contact arm moved through the complete arc and should make 
full and even contact for the entire distance. Remote control 
rheostats are operated by a ratchet and pawl actuated by a 
solenoid. This should work satisfactorily on 80 per cent of the 
voltage for which it is designed and should not jam on 120 
per cent. Motor-operated field rheostats should have a resist- 

343 



tance in multiple with the motor armature and another in series 
with the motor. The value of both of these resistances is 
determined by the Testing Department and after adjustment 
to give the travel in a specified time on normal voltage they 
should be tried on 80 per cent voltage, and with the above 
adjustment must give satisfactory and positive operation. 

Rheostats for Split Pole Synchronous Converters 

These are for use in the auxiliary field of synchronous 
converters and should have a load test as follows: Connect a 
suitable resistance in the circuit marked "field" and in series 
with this connect an ammeter of proper capacity. Turn the 
contact arm to the neutral position and apply voltage to the 
line terminals. The ammeter should read correctly when the 
arm is turned in one direction and should read backward for 
the other direction. This point must be checked for all rheostats 
of this type. 

Hand Operated, Starting and Regulating Rheostats 

In addition to the regular mechanical inspection, the arm 
should be brought to the first point and released to see if it 
returns promptly to the "off" position. This should also be 
tried from the running position. Regulating rheostats should 
be tried for holding and releasing in each position of the arm. 

All starting and regulating rheostats should be tried starting 
a motor several times and the release voltage noted. The arm 
must hold securely on half voltage. After this has been tried, 
full voltage should be applied. Then with the arm in the 
running position the line switch should be opened and the 
voltage at which the arm opens the circuit should be read. 
This must not exceed 35 per cent of the line voltage, but must 
operate before the motor has stopped. The retaining coil 
specification number should be checked and where an overload 
release is provided, the overload should be tripped and should 
release the arm immediately. The overload spool should after- 
wards be calibrated. See the drawing list for values. In the 
larger sizes which employ a contactor instead of a retaining 
magnet the contactor should be tested. (See instructions on 
"Contactor Testing" pages 345-6.) 

Automatic Starters 

These devices should receive a mechanical inspection; the 
contactor coil specification should be checked against the 
drawing list or Engineering Notice; all resistances should be 
measured and checked, and contactors tested (see instructions 
on "Contactor Testing" pages 345-6). Interlocks should be 
checked to see that they close in proper sequence with reference 
to the closing of the main contact tips of the contactor. All 
interlocks which are open should close, and those which are 
closed should open when the contactor closes. 

All sliding levers which are attached to dashpots should be 
moved by hand to see if they move smoothly and easily. There 

344 



should be no burred or pitted spots on the contact buttons 
or segments across which the contact arm moves. See also 
that the lever is properly retarded by its dashpot. Series con- 
tactors should be adjusted for the current values, as given in 
the Engineering Brief. Counter e.m.f. starters must be adjusted 
to pick up at the voltages specified, and after adjustment must 
be given an operating test with a motor of suitable rating. 

Alternating Current Panels 

Each panel should be given a test which represents the 
operating conditions as nearly as possible, and should be tried 
under different conditions, such as low voltage and high voltage. 
Where reversing features are provided, they should be tried 
thoroughly, and other special features should be given careful 
attention. For these tests the alternator should be held at 
normal voltage and frequency, except for the high and low volt- 
age tests. Automatic compensator panels should have the 
taps on the compensator read at the motor terminals. The 
magnetizing current should also be read at normal voltage and 
frequency, as this will furnish an additional check on the com- 
pensator coil. The XR number of the coil is stamped on a small 
piece of fiber and is imbedded in the coil surface. This number 
should be checked against the rating of the panel. If dashpots 
are employed, they should be adjusted for time as specified on 
the drawing list or Engineering Notice. This adjustment 
should be such that a greater time limit cannot be obtained 
in case the customer attempts to make readjustments. If this 
is not done, a burned coil may be the result. After this adjust- 
ment, the dashpot should be operated several times and the 
time checked to see that the adjustment is constant. A rough 
check on the temperature of the coils should be made by feeling 
each one after the voltage has been applied for a considerable 
time. 

Direct Current Panels 

As with alternating current panels, the operating conditions 
should be approximated or equaled where possible. All over- 
load, underload, field, and other relays should be calibrated 
and adjusted. Current limit relays should be adjusted and tried 
in all positions to see that they do not bind. Magnetic clutches 
should be adjusted by the factory and checked by the Testing 
Dept., and the operation on low voltage tried. Contactors 
should be adjusted (see below). The control circuits should 
be tried for normal operation, dashpots adjusted, and inter- 
locks checked as given previously. All panels, after having 
the circuits and resistances checked, should be connected to 
the motor and given a complete operating test. High potential 
tests should be applied after all other tests are completed. 
The terminal stamping should be checked. 

Contactors — Direct Current 

Contactors should have the resistance of the coil measured 
and recorded, the "pick-up" and "wipe" current checked, 

345 



also the amount of "wipe." If the wipe current is higher than 
the pick-up, this should be recorded separately. This current 
must not be greater than that specified in the Engineering 
Brief for the coil specification in use. Finger pressure, both initial 
and final, should be taken. The high potential test should be given 
after all other tests are completed and should be according to the 
Engineering Brief for both a-c. and d-c. contactors. 

Contactors — Alternating Current 

The resistance of the coils should be measured and recorded 
on the record of the panel. The coil specification, the "pick- 
up" and "wipe current," and the amount of wipe should be 
checked. Finger pressure, both initial and final, should be taken 
and the watts consumed by the contactor should be recorded 
and checked against the Engineering Brief. If an adjustable 
shading coil is used, it should be adjusted to give a watt value 
equal to, or lower than that specified in the Engineering Brief. 
The voltage and frequency should be held at normal for this 
test. The contactor must not hum at the minimum operating 
voltage given in the Engineering Brief, or at normal voltage. 
High potential tests should be applied after completion of 
the above test. 

Where a series resistance is used with contactors as a holding 
resistance, the contactor must pick up and wipe on 80 per cent 
of line voltage and remain sealed on this voltage with the series 
resistance in the circuit. When the contactor is open and the 
series resistance is in the circuit, the contactor must not pick 
up on 120 per cent of the line voltage, even with considerable 
vibration. The above does not apply where a series resistance 
is used other than as a holding resistance. 

Printing Press Controllers 

Each resistance should be measured and recorded. The 
circuits should be checked up and the contactors tested (see 
instructions on contactor testing). On two-motor equipments, 
the resistance should be checked as above and the pilot motor 
connected up. The time for a complete movement of the arm 
should be obtained at normal voltage with the variable pilot 
motor armature shunt resistance both all in and all out. See 
that the tripping of the overload opens the "stop" circuit of 
the control and immediately stops the equipment. Try the 
"safe" and "run " features of the push button stations. The small 
motor reversing switch should open the large motor control 
circuit when the small motor is reversed. All interlocks should 
be checked. On current limit controllers the master dial 
switch should be connected up and care should be taken to 
see that proper sequence of contactors is obtained. Try the 
current limit interlocks to see that they do not bind. Adjust 
the field relays according to the Engineering Notice. Calibrate 
the overload relay and check the wiring. The dynamic brake 
contactor should wipe with the motor running at minimum 
speed. 

346 



High Potential Tests 

All apparatus should receive a high potential test, as specified 
in the Engineering Brief. This varies with the class of apparatus. 

Shipment 

After the completion of the test, the name plates should 
be marked with the Testing Department's stamp and the 
wiring diagrams should be securely attached. 

There are occasionally special cases in which the diagram 
is to be mailed, in such cases the Head of the Section should 
obtain written permission from the Engineering Dept. to ship 
the apparatus without diagrams, and should attach a card 
marked "No connection diagram necessary." 

STARTING COMPENSATORS 

Compensators for starting Form K induction motors, 
synchronous motors, and synchronous converters are built 
for voltages from 110 to 13,200 volts. The switching mechanism 
and connections constitute the chief difference between the 
various forms. Forms A and B have double-throw oil 
switches which are so connected that the fuses, or overload 
relays, as the case may be, are in the circuit only when the motor 
is thrown on the line. (See Figs. 154 to 159 inc.) The figures 
show the connections for the Forms A and B two-phase and 
three-phase compensators with the necessary overload and 
no-voltage relays. The tests required are ratio, magnetizing 
current, heat runs when specified, double potential and high 
potential. The no-voltage release coil should, in addition 
to the double potential and high potential tests, receive pick-up 
and releasing tests and have its resistance measured. The 
oil boxes should be removed and the switches carefully examined 
before making any tests. 

On compensators above 550 volts the oil switch must not 
be used to break the magnetizing current unless the oil box is 
filled with oil as the switch will arc across and not open the circuit. 

Complete tests on compensators consist of commercial tests, 
heat runs, impedance, and insulation tests. 

Commercial tests consist of ratio of taps, exciting current 
at normal voltage and frequency, and insulation tests. 

Insulation tests consist of applying high potential between 
the windings and ground for one minute, operating the com- 
pensator at double potential for one minute and also at one 
and one-half times normal potential for five minutes. 

Ratio 

Connect the line leads to the terminals on the testing stand. 
These terminals are connected in multiple by busbars at the 
back of the terminal board. Apply 100 volts to the lines; 
throw the switch on the compensator under test to the "starting " 
position, leaving all others in the "off" position. On the three- 
phase compensator read the voltage between the taps (the 

347 



6 A A' A' A B 



Phased 




Phase* Phases 



Fig. 154 
CONNECTIONS OF QUARTER-PHASE, TYPE IQ, INDUCTION MOTOR 
AND TYPE NR, FORM A2 STARTING COMPENSATOR 
WITH NO-VOLTAGE RELEASE ONLY 



P/?aseA « 



Generator 



Over/ood 
/?e/ays 



/?e/ay 



rff 



Connect ie/ow tens/on c/rcu/t 
w/j/c/> t*ot//d£>e aVfecteaf /n 
case or^oz/ure or^o/tape 

on motor or- tnroupn 
tran&for/ner to motor /cads 



Cat>/e 
C/a/np 




SacAr 
f/nper B/oc/c 



CyZ/rtcfer 



front 
/7/?aerfi/oc# 




Fig. 155 
CONNECTIONS OF QUARTER-PHASE HIGH VOLTAGE TYPE NR 
STARTING COMPENSATOR WITH NO-VOLTAGE AND 
OVERLOAD RELAY 



348 




Fig. 156 
CONNECTIONS OF THREE-PHASE, TYPE I, INDUCTION MOTOR 
AND TYPE NR, FORM A2 STARTING COMPENSATOR WITH 
NO-VOLTAGE RELEASE ONLY 




Generator 



Fig. 157 
CONNECTIONS OF THREE-PHASE TYPE I, INDUCTION MOTOR 
AND TYPE NR, FORM A3 STARTING COMPENSATOR, WITH 
NO-VOLTAGE AND OVERLOAD RELEASE 



349 




Connect to a /otv tens/on circuit lyh/ch 
wot/A* be affected /n case of faik//e 
of yo/tage on the motor or through 
transformer to motor /eads 




Fig. 158 
CONNECTIONS OF CR HIGH VOLTAGE THREE-PHASE STARTING 
COMPENSATOR WITH NO-VOLTAGE AND 
OVERLOAD RELEASE 







Fig. 159 
CONNECTIONS OF QUARTER-PHASE, TYPE IQ, INDUCTION MOTOR 
AND TYPE NR, FORM A3 STARTING COMPENSATOR WITH 
NO-VOLTAGE AND OVERLOAD RELEASE 



350 



lowest voltage tap is next to the core). Standard compensators 
for motors up to and including 17 h.p. have 50, 65, and 80 per 
cent taps; those for motors above 17 h.p. have 40, 58, 70 and 
85 per cent taps. The ratios obtained should agree to within 
3 per cent of the above. 

In determining ratios see that both the primary and 
secondary instruments are on the same phase. In checking the 
ratio of quarter-phase compensators, join leads A' and A' 
(see Fig. 154), apply 100 volts to the lines A and A, and read 
the voltage on the taps between the motor leads B, B and each 
tap. These compensators are tested "open delta." 

Magnetizing Current 

Magnetizing current is measured at normal primary voltage 
and frequency. The alternator used should operate at normal 
voltage. The exciting current at normal voltage and frequency 
should, on 60 cycle compensators, not exceed 25 per cent, and, 
for 40 and 25 cycle compensators, it should not exceed 30 per 
cent of the full load current of the motor, assuming in the 
smaller sizes, the motor to operate at 75 per cent efficiency 
and in the larger sizes at 80 per cent. 

On special compensators, covered by Engineering Notices, 
the magnetizing current should be taken at 20 per cent above 
normal potential as well as at normal. In making this test 
hold the voltage constant across one phase and read the current 
in all three legs, then hold the current constant in one leg and 
read the three-phase voltage, or instead of holding current in 
one leg, two voltmeters may be used, one to hold the voltage 
constant, and the other to read the three-phase voltage. Owing 
to the fact that these machines are used for starting duty only, 
a high current and magnetic density is employed. Therefore, 
a very small change in frequency or potential makes a con- 
siderable difference in the exciting current, and care must be 
exercised to see that the voltage and frequency are normal. 
Quarter-phase compensators are tested "open delta." 

It will be noted that on three-phase compensators one leg 
will read slightly lower than the other two, which should be 
balanced. This is due to leakage caused by the high magnetic 
density and the close proximity of the iron case and supporting 
straps. 

Heat Runs 

Short-circuit the motor leads and apply sufficient voltage 
to the line leads to force the required current through the 
coils. This current should be held constant for one minute 
and the impedance volts read in each phase during this period 
and on each set of taps. The value of the current will be given 
in the standard Engineering Brief, or in Engineering Notices 
covering special cases. Thirty minutes should elapse between 
successive heat runs on the same compensator up to and in- 
cluding 200 h.p. ; above this size one hour should be allowed. 
A thermometer should be placed on each coil and the temper- 

351 



atures watched until they attain a maximum after each run 
and this value should be recorded. Directly after the close 
of each run the tap leads should be changed to the next tap. 
Heat runs should always be started on the tap next to the core. 

On large compensators it sometimes happens that there is 
not sufficient power available to make the heat run as called 
for. In this case upon permission from the Engineering Dept. 
the following alternative may be used: 

Hold half the current called for, and hold it four times as 
long. This will give an equivalent heating. 

After the completion of the heat run the taps should be taped 
up after placing the tap leads on the second set of taps. All 
compensators should be sent out with the tap leads on this 
tap. 

Insulation Tests 

The double potential and the high potential tests should be 
applied after all other tests are completed and the compensator 
is assembled with the taps taped up. The frequency should be 
high in order to keep the magnetizing current below the normal 
current for which the compensator is designed. In case the 
normal voltage of the compensator is so high that it is impossible 
to secure double potential, one set of taps may be connected 
to the line and voltage applied, which shall be double the voltage 
for which the tap is designed. 

All compensators up to and including 550 volts normal rating 
should receive 2500 volts insulation tests from windings to core 
and frame for one minute; those from 550 to 4000 volts should 
receive 7500 volts; those for 4000 volts should receive 10,000 
volts; those above 4000 volts, double normal potential. In 
applying the high potential tests all leads should be connected 
together. 



352 



CHAPTER 20 

MINE AND INDUSTRIAL LOCOMOTIVES 

MINING LOCOMOTIVES 

Mining locomotives (LM type) are built for various gauges 
in sizes of 3 to 20 tons. With, the exception of an occasional 
3-motor, 6-wheel type they are all 2-motor, 4-wheel locomotives 
and are equipped with either 250 or 500 volt series wound, totally 
enclosed motors mounted directly on the axles and driving 
through double reduction gearing. The controllers are of the 
"R" type, which have a separate cylinder for forward and 
reverse in which is incorporated a commutating switch that 
permits starting the locomotive with motors either in series 
or in parallel. 

Before being sent to the Locomotive Department the various 
parts of the equipment are tested separately; the motors being 
subjected to the standard test for railway motors and the con- 
trollers, circuit breaker, etc. being subjected to the regular 
tests in force in their respective departments. The test of the 
locomotive proper is, therefore, principally a bearing run, a 
check of the wiring connections and a general inspection to see 
that all parts operate properly, that clearances are sufficient 
and that the apparatus is properly located. 

Unless otherwise specified, tests should be conducted as 
follows: 

1. Anchor the locomotive securely on the testing stand 
that is provided in the Locomotive Section and operate it on 
all points of the controller, forward and reverse, both series and 
parallel, to assure that connections have been properly made. 

Caution: As these are series motors running practically 
without load, power should be thrown off as quickly as possible 
when checking with the controller in the "parallel" position. 

2. Make a bearing run of 15 minutes duration in each 
direction at full "series" position of the controller. 

3. Measure and record the resistances of the several 
rheostat steps. A 20 per cent variation from the values given 
in the DS print is allowable. 

4. Make a careful general inspection to see that the brakes, 
sand rigging, headlights and circuit breaker operate properly; 
that the wiring cables are clamped securely and that they do 
not interfere with the access to the motor bearings or other 
parts; see that the rheostat terminals have good clearances to 
"ground" on the locomotive frame and check up carefully all 
questions on the testing record. 

Cable Reels 

Many locomotives, particularly the 5 and 6 ton sizes are 
equipped with motor-driven cable reels. The purpose of the 
reel is to permit operation over those portions of the mine 
roads that are not provided with trolley wires. The reel 

353 



rotates with its axis vertical and is driven by a four pole, series 
wound, vertical motor which is wired directly across the line 
in series with a permanent resistance to protect it from an 
injurious rush of current when the motor is stalled. The outer 
end of the cable is hooked over the trolley wire and as the 
locomotive moves forward the reel motor is overhauled and 
acts as a series generator, its counter torque producing sufficient 
tension in the cable to pay it out evenly. As soon as the loco- 
motive starts back and slackens up on the cable, the motor 
action comes into play and winds up the cable; the action is 
analogous to that of a spring having infinite length. 
Test as follows: 

1. Measure and record the cold resistance of the armature, 
field and permanent rheostat. 

2. Check the polarity. 

3. Check for satisfactory operation by mounting the reel 
equipment on the shop locomotive that is provided for this 
purpose and run it out on the test track. At least five trials 
should be made running the full length of the cable. The 
reel should pick up and wind the cable compactly when the 
locomotive is running on the full series point of the controller. 

4. When the reel equipment is mounted on its own loco- 
motive, check the rotation (looking at the top of the reel) as 
follows: If the motorman's seat is on the left hand side of the 
locomotive the rotation should be counter-clockwise. If the 
seat is on the right hand side of the locomotive the rotation 
should be clockwise. 

Winding Devices 

For hauling cars out of mine slopes where the grade is too 
steep for locomotive operation some locomotives are equipped 
with winding devices. These consist of a vertical axis cable 
drum fitted with 400 to 600 ft. of flexible steel cable and driven 
by a series wound, totally enclosed motor. 

Test as follows: 

1. Give the drum and motor a 15 minute bearing run, 
holding them down to moderate speed by applying the band 
brake on the drum. 

2. See that the brake and clutch levers operate readily 
and that the clutch engages properly. 

3. With the clutch disengaged, see that the cable can be 
hauled out by hand easily. Use a spring balance and record 
the pull required; this must not exceed 45 lb. 

4. Measure and record the resistance of the starting 
rheostat. 

INDUSTRIAL LOCOMOTIVES 

Industrial locomotives (LS type) are built for various 
gauges and in sizes from 3 to 25 tons. They are practically 
all of the single truck, 4-wheel, 2-motor type. The electrical 
equipment in general is the same as for the mine locomotives 
and they differ only in the mechanical arrangement of the 

354 



frames. With the exception of the larger sizes (15 to 25 tons) 
the test should be conducted in the same manner as for the 
mining locomotives. Those of 15 tons and above are, as a rule, 
built for the standard gauge (56 3^2 in.) and are equipped with 
cabs, air brakes and MCB couplers. Instead of using the 
testing stand in the Locomotive Section, these should be tested 
on the General Electric Company test tracks and the general 
instructions in force there will apply. 

STORAGE BATTERY LOCOMOTIVES 

Storage battery locomotives (C.S.B. and L.S.B. types) are 
at present built in various sizes, from 2^ to 8 tons. These 
as a rule will be single truck, 4 wheels, with either one or two 
motors, and for various gauges from 24 in. to 563^ in. 

The equipment differs from the standard mine (L.M.), and 
industrial (L.S.) types, in having low voltage automobile type 
motors, driving the wheels by double reduction gearing in 
place of the regular 250-500 volt motors. The storage battery 
will usually consist of 44 "lead acid" cells or 70 to 80 Edison 
cells, all connected in series for an average discharge potential 
of 85 volts. 

After the battery is in proper condition of charge as herein- 
after described, the locomotive should be placed on the testing 
stand and test conducted in the same manner as before described 
for mining (L.M.) and industrial (L.S.) type, i.e., operate on 
all points of the controller forward and reverse to see that all 
connections are properly made, make 15 minute bearing runs 
in each direction; measure the resistance of the rheostat; and 
make a general mechanical inspection of brakes, sand rigging, 
headlights, wiring, etc. 

When a locomotive has been delivered to test, each and 
every cell should be carefully inspected to see that the electro- 
lyte is at the proper level. This level varies for the different 
types and makes. For the "Lead Acid" battery (distinguished 
by a rubber jar) the level of the liquid should be Y2 in. above 
the plate, for the Edison (distinguished by metal jars) the 
level of the liquid should be Y2 in. above the plates for the 
A-4 and A-6 types, and y % in. for the A-8, A-10 and A-12 types. 

Caution: Gas may be present in the cells. Do not use a 
match, candle or other open flame to inspect. 

The lead cell batteries may be easily inspected by removing 
the cover or the soft rubber plug. For determining the height 
of liquid in Edison cells the method illustrated in Fig. 160 will 
be found convenient. 

If the liquid is low, sufficient pure distilled, water should be 
added; never use water suspected of containing the slightest 
impurities as very great damage to the battery may result. 

After ascertaining if the liquid is at the proper height see 
that the several battery trays or crates are properly connected 
in series, as otherwise a portion of the battery might easily be 
ruined. 

355 



Since it is impossible here completely to describe the various 
methods of charging the several types of batteries, due to the 
fact that the several manufacturers recommend slightly different 
procedure, the following brief summary must suffice for the 
first charge while the battery is temporarily in our care: The 
battery should be placed on charge at the normal rate as given 
with the instructions that accompany each battery. For lead 




Fig. 160 

QUICK METHOD OF DETERMINING PROPER LEVEL OF 

ELECTROLYTE ABOVE PLATES 



batteries when the voltage has reached a value of 2.55 volts 
per cell (112 volts for 44 cells) the charging should be discon- 
tinued. For Edison batteries, charge at the normal rate as given 
on the name plate for 7 hours or until the voltage has reached 
a value corresponding to 1.85 volts per cell. 

When all tests have been completed, the locomotive may be 
shipped without recharging, as the running light test will as a 
rule use but little of the battery charge. 

Fig. 161 shows the proper method of connecting a battery 
to the line for charging. 

356 



Vo/t meter Ammeter 







Fig. 161 
DIAGRAM SHOWING GENERAL METHOD OF CHARGING BATTERIES 

The trays are first connected in series, i.e., the. negative of one tray to the 
positive of the adjoining tray. The current flows from the positive wire of the 
current supply, into the positive terminal of the first tray (in this case on the 
right) ; through the positive and out of the negative of each cell and each tray 
in turn and returns to the current supply from the negative of the last cell. 

The voltmeter is connected inside the resistance or rheostat, to show the 
battery voltage only. 



357 



CHAPTER 21 

PORCELAIN INSULATORS 

Insulators are of two distinct types; link insulators and 
bushings. 

The Link Insulators are those used for either strain or 
suspension work and have holes, called cableways, for fastening 
the cables. 

Bushings comprise all other kinds of porcelain insulators 
which are cylindrical in form, and serve as conduits. 

Inspection 

Before testing, all insulators should be given a rigid inspec- 
tion for mechanical defects, such as cracks, flaws, warping, 
chipping and non-uniformity in color of glaze. 

Methods Used in Applying High Potential 

In applying high potential to porcelain insulators, they 
are placed on a rack which holds twelve, and these are tested 
together. 

In the larger type requiring a special test, it will be found 
advantageous to use two racks at once. 

The Link Insulators have cableways on either side between 
which the potential is applied. 

This can be done by using two spiral springs which can be 
pushed through the cableways and hooked upon themselves, 
thus making the insulator take the same position as it does 
in service. 

In testing bushings, a pipe or spring is laid through the 
center of approximately the same size as the hole. A piece 
of metal foil or spring is then wound around the outside at the 
middle point. The potential test is then applied between the 
metal parts. 

Routine Potential Tests on Insulators for Switchboard Depart- 
ment 

Potential values, where called for, should be determined by 
the needle gap and striking distance curve C-845. (See Fig. 186.) 
This determination should be made under testing conditions 
with the insulators connected to the transformer. (The capacity 
currents taken by some insulators and the oscillating discharge 
passing over their surface sometimes seriously affect the trans- 
formation ratio.) Where arc-over values only are specified, 
the tester must see that the testing outfit and conditions will 
not facilitate arc-overs. 

Insulators in production and not listed in Eng. Brief 10761A 
should be called to the attention of the Engineering Department. 

Any insulators listed showing serious discrepancies from 
the results of specified tests, without defects being apparent, 
should be referred to the Engineering Department before 
proceeding further. 

358 



Tests are called for by letters having the following signifi- 
cance: 

11 A" Apply potential between central stud filling the 
insulator bore, and the foil band around the outside of insulator. 
Foil should be so located as to bring the maximum tax (stress) 
through that section of the insulator which is under maximum 
stress in service. If the outer surface is not completely glazed 
foil should be placed on the unglazed surface. 

" B " Includes ' ' Blind ' ' Insulators. Apply potential between 
the stud and foil around the opposite end of insulator, the foil 
being located to give approximately service conditions. 

" C" Apply potential between foil located inside and 
outside the insulator on the unglazed parts. 

"D" Apply potential between spiral springs coiled in 
cableways. 

".4," "B," " C" and "D" tests consist of a flash-over 
voltage applied instantaneously and a 90 per cent flash-over 
voltage applied for 30 seconds. 

TUBES 

Wet process porcelain tubes must be tested at 20,000 volts 
per each y% in. thickness applied for 30 seconds between central 
stud and foil covering the outside completely except at ends 
where the foil is omitted to obtain the necessary striking dis- 
tance. 



359 



CHAPTER 22 

TRAIN CONTROL APPARATUS 

Inspection and High Potential Tests 

Before testing any apparatus, a careful inspection must be 
made for any mechanical defects. Any part of apparatus that 
will be subjected to a difference of potential must be given a 
high potential test, corresponding to that specified in the 
Engineering Briefs. 

AIR BRAKE APPARATUS 

This includes valves, governors, strainers, cylinders, and 
all other parts that make up the braking system of a car or 
train. 

VALVES 

Air valves are manufactured under the following type 
letters: A, S, VL, E, and TE. 

The A and S are motorman's valves, different forms of 
which are used for straight air and emergency brake systems. 

The VL is a pressure reducing valve used for automatic 
air brake systems, and reduces the main air reservoir pressure 
to a lower and constant pressure. 

Type E includes all emergency valves. One of the most 
important is the Form E, used with automatic air brake systems 
in connection with the pilot valve located in the controller. 
It exhausts the train pipe whenever the pilot valve is opened, 
thus applying the brakes to the car or train. 

Magnet valves are included under the Type TE. They are 
used for remote control. The Form B is used for operating 
pantograph trolleys. 

Mechanical Inspection 

Each valve is given a careful inspection to see that all the 
pipe connections have good threads. In the Types A and S, 
the fit of the handle should not be too loose. There should be 
only enough clearance to allow it to be easily removed. The 
handle should move over the different positions with compara- 
tive ease and be removable only in the lap position. 

Air Valve Tests 

Every casting, which will be subjected to air pressure in 
service, should be tested for porosity. This is done by immersing 
the casting under pressure in water. Where this cannot be 
done, cover the casting, under air pressure, with soap suds. 
Water must be used in every case to determine the amount of 
leakage, and all castings showing a continuous leakage must 
be rejected. 

After assembly, each valve should be subjected to an air 
pressure and operated as near as possible at the service pressure. 
All parts should then be again tested for leaks by immersing 

360 



in water or by covering the part with soap suds, while under 
pressure. 

Valves with metal stem seats are provided with ground 
stems. The stem and hood are inspected before being assembled 
on the valve body. 

GOVERNORS 

Governors automatically keep the air pressure of the braking 
system within a certain range by opening and closing the com- 
pressor motor circuit. 

Operating Test 

Each governor is stamped with the type letters and numbers; 
the letters represent the style of the governor, and the numbers 
represent the capacity and range at which it will operate. The 
first number indicates the minimum opening pressure in pounds 
per square inch. The second number denotes the maximum 
opening pressure. The third denotes the variation in the opening 
and closing pressures. The tests are similar in all governors 
and consist of connecting them to a source of compressed air, 
the compressor motor circuit being wired through the governor 
tested. The governor should then be adjusted to open the 
circuit at the minimum opening pressure and close it as soon as 
the pressure is reduced by an amount equal to the given pressure 
range. It must then be tested for maximum opening pressure 
and should again close when the pressure is varied through the 
amount equal to the normal range. 

All parts under pressure should be examined for leaks. 

Type ME 65-100-10 Form A Governor 

This governor is designed for use with a large compressor, 
the circuit of which is made or broken by a contactor or con- 
tactors controlled by the governor. The test is similar to 
that given above, except that the main circuit of the com- 
pressor is broken by the contactors controlled by the governor 
instead of by the governor direct. 

STRAINERS 

Strainers are used in air brake systems to catch scale and 
small particles that would interfere with the operation of any 
of the apparatus. They are tested with air pressure and exam- 
ined for leaks. 

CONTROLLERS 

The R, K, C and T controllers comprise the principal types, 
All others are modifications of the above. 

• The R and K types make and break the main motor circuit 
within the controller. 

The Type C controller makes and breaks a circuit which 
operates contactors that open and close the motor circuits. 
With a contactor box on each car and the control circuits 
connected in parallel, the motor circuits for a whole train can be 
controlled with one controller. 

Type T is used with induction motors, generally being used 
to cut out resistance in the rotor circuit of Type M motors. 

361 



Inspection 

The development of each cylinder and its fingers should be 
examined to see that they check with the DS diagram. The 
fingers should make good contact on the segments of the cylinder 
and in the order shown. Controllers having several auxiliary 
fingers in series should be tested to see that these fingers make 
and break contact simultaneously. All auxiliary release knobs 
should open the auxiliary contact fingers when released at any 
position of the handle. -The main cylinder and reversing cylinder 
should interlock, so that the reversing handle cannot be thrown 
when the controller is in any but the "off" position. When the 
reversing handle is in the removable position, the main cylinder 
should be locked in the "off" position. All controllers should 
receive a careful inspection for mechanical defects. All cables 
passing through the frame of the controller should pass through 
an insulating bushing, except in the case of Type R controllers 
for mining locomotives. 

There should be sufficient clearance between points at 
different potentials and between all current-carrying parts and 
frame. 

Operating Test 

All controllers should be connected and operated under 
service conditions as nearly as possible. Those controllers 
which operate the main motor circuit should be connected 
and operated with a motor or motors with the proper resistance 
in circuit, to check the wiring and the blow-outs on the different 
fingers. Carefully note whether the arc blows in the proper 
direction and ruptures satisfactorily when turning the con- 
troller to the "off" position. When the controller is not adapted 
to motors used in the testing department, the complete develop- 
ment and wiring of the controller should be carefully checked 
with the DS diagram. Those built to operate contactors should 
be connected to the latter and operated, noting the direction 
the arc blows as in other controllers. When turning the con- 
troller to the "on" position the auxiliary finger or fingers should 
make contact first, and should break last when turning to the 
"off" position, unless otherwise stated on the Engineering Brief 
for that particular type or form of controller. 

Where a separate blow-out is used for the auxiliary fingers, 
it should be carefully tested. The auxiliary fingers, whether 
fitted with a blow-out coil or not, should break the total current 
of the controller in any position, when the auxiliary release 
knob is released. 

Automatic and Semi-Automatic Controllers 

Several types of the C controllers have their cylinders 
fitted with a spring and governor so that when the handle of 
the controller is turned to the "full on" position, the spring is 
wound up sufficiently to rotate the cylinder. The governor 
should be adjusted so that the cylinder will rotate in the specified 
time. The governor is fitted with a small magnet coil which 

362 



should lock and hold the cylinder in any position when the 
specified current is passed through the coil. 

Pilot Valves 

Many C controllers are fitted with pilot valves operated 
by the auxiliary release knob. This pilot operates a valve for 
an emergency operation of the brakes. They should be con- 
nected to an emergency valve which should trip whenever the 
auxiliary release knob is released. The reversing handle should 
interlock with the valve in the "off" position, and should prevent 
tripping of the emergency valve. The valve should operate 
quickly without leakage when closed. 

REVERSERS 

Reversers used in Type M control are operated by solenoids 
energized through the reversing cylinder to the controller. 
The segments on the rocker arm are so arranged that a move- 
ment from one extreme position to the other changes connections 
and reverses the armature or field circuits of the motors. 

Operating Test 

The operating test consists of connecting the inductive 
resistance specified between the first and third fingers, one side 
of the shop to the third finger, with the other side connected 
alternately to the two solenoid coils. Under these conditions 
the reverser should operate quickly and throw completely over, 
without rebounding. It should be operated on the different 
voltages specified. The arc formed on the control fingers must 
be blown outward from the fingers and should rupture immedi- 
ately. This should be noted. The coil resistances should be 
measured and should check within 10 per cent of that specified 
in the Engineering Briefs. 

Spools for Supply Shipments 

After the high potential test, the resistance of each spool 
should be measured and should check within 8 per cent either 
way, from that specified in the Engineering Briefs. 

MS SWITCHES 

MS switches are made up for the control of various car or 
train circuits, and are in most instances equipped with magnetic 
blowouts. Quick-break operation on some types is also employed. 

Each switch should be examined for mechanical defects 
such as broken or loose parts. The switch should work freely 
and should not stick or bind in any position. It should make 
good contact when closed. 

Switches designed to open the main current should be 
given a blow-out test, consisting of breaking a specified current 
in order to see that the arc is blown outward, and ruptures 
satisfactorily. All switches should be given a high potential 
test between parts of opposite polarity when a blade or blades 
are open. 

363 



CUT-OUTS 

Cut-outs for train control service are used to cut out the 
control circuits of individual cars from the rest of the train, one 
cut-out being placed on each car. 

Besides seeing that the fingers make good- contact on the 
contact segments, all fuses should be "rung out" to see that 
they are in good condition. 

CONNECTION BOXES 

Connection boxes are used as splicing junctions where the 
wiring of the car is run through conduit. They consist of a 
metal box containing connection terminals to which wires 
may be easily connected or disconnected. They receive a 
high potential test only. 

MU TRIPPING SWITCHES 

These switches have a series coil through which the motor 
circuit is wired, and a small control switch through which the 
control circuit for the line contactors is wired. 

The series coil operates an armature fitted with a calibrated 
spring similar to a circuit breaker, so that if an excess of current 
is taken by the motors, the armature trips out the control circuit 
switch, opening the contactors in the motor circuit. Examine 
the compound box to see that it is not cracked or broken, and 
that all flat headed screws are center punched other than the 
removable screws used in fastening the cables. 

The control switch should work freely and make good 
contact when closed. 

The switch should open when the lever is thrown to the 
"off" position. 

All MU switches are calibrated for various tripping points. 
(See Engineering Briefs.) They are sent to the Test Dept. for 
calibration without the cover. The armature should be held 
in the operating position by means of a block of fiber or other 
non-magnetic substance, as though it rested against the cover. 
Marks are made to determine the relative positions of the cap 
of the calibrating springs for the different currents. The switches 
are then returned to the shop for stamping and assembly of 
cover, after which they are given a blow-out test, which consists 
of breaking a small inductive circuit with the switch to deter- 
mine the direction of the blow-out. 

A high potential test should be made between the series 
coil and the control switch, also between the switch blade and 
upper left-hand terminal when the switch is open. 

CONTACTORS 

Contactors are used for making and breaking the motor 
circuits on a car. They are operated by a solenoid which 
actuates a lever carrying one contact tip, the other tip is 
stationary, and iitted with a blow-out coil which helps to break 
the arc between the tips. 

364 



There are two distinct types of contactors: DB contactors 
which are used for direct current work, and DBA contactors 
which are used for alternating current work. 

The DBA contactors have a laminated armature and an E- 
or U-shaped laminated field with copper shading coils in the face 
of the outside leg, to prevent humming when the contactor is 
closed. 

An arbitrary number is assigned to each contactor, and form 
letters are used to indicate minor mechanical differences. A 
numeral follows the form letter to indicate the operating coil 
used, viz. DB-260-A-1. 

Inspection 

Each contactor should be examined carefully for mechanical 
defects, such as broken arc chutes, cotter pins, loose screws or 
bolts. Also note whether it bears the Mechanical Inspection 
Department's stamp. The contact tips when closed should 
make good contact over their full width. The copper shunt 
should be free from sharp kinks or bends and should not rub 
on any metal part having sharp or rough edges. All contac- 
tors must operate freely, and must not stick or bind in any 
position. 

TYPE DB CONTACTOR 

Commercial Tests 

From the tables given in the Engineering Briefs, see that 
specification on the spool corresponds with the stamping on 
the name plate. 

When hung in the proper position, the contactor should 
pick up and wipe contact at or below the current values given 
for the respective spools, care being taken that the contactor 
wipes full contact, as sometimes the pick up current is taken 
to be the same as that required for the wipe contact. To avoid 
this error, note that the first upward movement of the plunger 
only brings the contact tips together. This is called the pick 
up. The next movement wipes the contacts over one another, 
and also increases the pressure between them. The amount of 
this movement should equal or exceed that given in the Engi- 
neering Brief. 

Measurement of Spring Pressure 

Insert a strip of paper or cloth between the tips, and put 
enough current through the operating coil to close the contactor 
completely. 

Hang a spring balance from the screw heads holding the 
tip on the finger, and note the pull required on the spring 
balance to loosen the paper between the tips. 

Resistance Measurement of Spools 

The resistance of each coil should be measured and be 
within 8 per cent above or below the specified resistance at 25 
deg. cent. 

365 



TYPE DBA CONTACTOR 

The pick up and wipe is similar to that in the DB contactors. 
As each DBA contactor, however, is connected directly across 
the line, it is tested for the operating voltage instead of the 
current. The voltage should be obtained by gradually raising 
the field on the alternator. 

The magnetizing current is measured at the proper frequency, 
and should be taken with the armature fully closed. 

The finger pressure should be taken as in the DB type. See 
that the contactor wipes on the same voltage at which it picks 
up. It should do so to protect the tips from freezing (welding 
together) due to insufficient contact area. The operating coil 
would also burn out, since with a-c. contactors the current is 
high until the contactor is closed. After the contactor has 
wiped, it should be perfectly noiseless. 

SPECIAL TESTS 

The test sheet should contain the following data: 
Coil specification (No. of turns and size of wire). Cold 
resistance and temperature of coil at which the cold resistance 
is taken. Number of coils in series or multiple during test. 

Finger Pressure 

This test is made by holding the contact fingers at full 
wipe position, attaching a spring balance to the screw which 
holds the finger to the jaw by means of a small loop of wire. 
A pull is then exerted through the spring balance until the 
fingers separate sufficiently to allow a thin strip of paper, 
placed between them, to be drawn out. The pull as recorded 
by the spring balance is taken as the finger pressure. The 
pressure of each finger should be measured separately. 

"Minimum Pick Up" and "Wipe" 

A contactor is at "pick up" position, when the armature 
is raised so that the fingers just make contact. At "wipe" 
position the contactor is fully closed. 

On a-c. contactors, two additional tests, regulation of alter- 
nator, and chattering and drop-out voltage are made in connection 
with the minimum pick up test. 

Regulation of Alternator 

With the armature blocked open, read the speed and voltage 
of the alternator both with and without the contactor in circuit. 
Repeat with the contactor blocked shut. 

Chattering and Drop-Out Voltage 

With the contactor picked up and fully wiped, note the 
minimum to which the voltage can be reduced before the con- 
tactor becomes noisy, and also note the voltage at which the 
contactor opens. 

366 



Saturation Curve 

This curve is taken at different voltages reading amperes 
and watts, readings being made both with the contactor closed 
and opened, or at such air-gaps as special instructions may 
require. 

Pull Curves on D-C. Contactors 

This curve is taken by holding a constant current and 
reading the pounds pull for different air gaps. The curve is 
taken in either of the following ways: 

First: By carefully adjusting the air gap, weighting down 
the plunger, and holding the amperes constant while weights 
are subtracted from the plunger until it picks up. 

Second: By weighting down the plunger and holding the 
amperes constant, while the air gap is gradually decreased 
until the plunger picks up. The air gap is then measured. 
A variation of this curve is sometimes made by holding a con- 
stant air gap and varying the amperes and weights. In connec- 
tion with the data for these curves, the length, diameter and 
weight on plunger should be given; the length of plunger being 
taken as the length from the butt end to the center of the hole 
in the lower end. The weight given in the table should be 
exclusive of the plunger and should be so stated on the Test 
Sheet. 

Pull Curves on A-C. Contactors 

The method of taking a pull curve on an a-c. contactor 
is more complex than on a d-c. contactor. In either case the 
pounds pull is dependent upon the ampere turns. In a d-c. 
contactor, however, the amperes at any voltage varies directly 
with the resistance of the coil and is independent of the plunger 
air gap, whereas in an a-c. contactor the amperes at any voltage 
does not vary with the resistance, but with the impedance. 
The reactance varies with the armature air gap. For this 
reason it is not desirable to hold the amperes constant. If, 
however, the voltage is held constant, an error will be caused 
due to the resistance of the coil being increased by heating. 

In tests where great accuracy is required, this error can be 
eliminated and all contactors can be compared upon a common 
basis by the following method: 

First: Measure the resistance of the coil cold. 

Second: Holding the voltage constant at that value at 
which the pull curve is desired, take an ampere air gap curve; 
i.e., read amperes at various air gaps. This curve should be 
taken as rapidly as possible to avoid undue heating of the coil. 

Third: Take a check reading of the resistance to see if 
the coil has been much heated. If the heating is slight, an 
average of the two readings should be taken as the resistance 
of the coil. 

Fourth: The ampere air gap curve thus obtained should be 
corrected for a temperature of 25 deg. cent, and replotted. 

367 



Fifth: Take a pull curve as given by the first method for 
d-c. contactors, holding the amperes constant corresponding 
to the different air gaps as obtained from the corrected ampere- 
air gap curve. 

In cases where the cold temperature of the coil happens to be 
within a few degrees of 25 deg. cent, the pull curve can be taken 
directly, holding the voltage at the value at which the curve is 
desired. Great care should be taken to prevent undue heating 
of the coil. The current must be on only for a sufficient time 
to obtain readings. At the completion of the test take another 
check reading of the resistance to determine the heating. 

Work Curve 

This curve is taken by measuring the pounds pull necessary 
to lift the plunger or armature at different air gaps, having 
the complete operating mechanism of the contactor and spring 
adjusted to give the finger pressure required. 

Speed Curve 

Speed curves are taken on contactors and relays to deter- 
mine the time a contactor takes to close or to open. 

For taking this curve, a special mechanism has been made 
which operates as follows: The contactor is set on a special 
stand and a mechanism is then fitted to the plunger of the 
contactor so that a pencil attachment operates along a vertical 
line. The pencil bears upon a sheet of sensitive paper which 
is secured to a cylindrical drum, revolving about a vertical 
axis. The drum is rotated by a small shunt motor operating 
at constant speed. Upon the periphery of the drum, contact 
fingers are fastened, which make and break the circuit through 
the contactor coil. The contactor is then operated through a 
number of cycles, and the mean curve is drawn. In this test 
the required voltage must be held across the coil without resist- 
ance in series, on account of the inductance of the circuit. 

Heat Runs 

This test is very similar to the heat runs made on other 
apparatus and consists in measuring the temperature of the 
coil or other part at frequent intervals, both by thermometer 
and resistance. It should be noted that, as the operating coils 
are well wrapped with twine or other binding, thermometers 
placed on the outside of the coils do not give a fair indication 
of the temperature of the interior of the coil. For this reason 
the temperature must be calculated from the rise of resistance. 
To get these readings as accurate as possible, care should be 
taken in measuring the cold resistance. All heat runs on coils 
should be made with coils assembled in the contactor frame, 
unless otherwise specified. All heat runs should be made holding 
the voltage constant. 

Life Tests 

Life tests on contactors are made generally to determine the 
effect of service on the wearing qualities of the various parts. 

368 



Before starting the test, the diameter of the hinge pins and 
hinge pin bearings, the maximum air gap, finger pressure, and 
all other parts of the contactor that will be affected by service, 
should be carefully measured. During the test a daily record 
should be kept of the number of operations, and of the operating 
failures of any of the parts. At the completion of the test, 
the parts measured at the beginning must be again measured 
to determine the amount of wear. 

FUSE BOXES 
Commercial Tests 

Fuse boxes are made of fiber or compound, and are fitted 
with terminal blocks, in which ribbon fuses may be readily 
placed. 

The principal test is high potential, for the value of which 
see Engineering Briefs. 

Fuse Boxes with Magnetic Blowout 

After the high potential test, a small fuse is placed across 
the terminal of these boxes. A current is then passed of suffi- 
cient capacity, and at sufficient voltage, to blow the fuse immed- 
iately. This is done to determine the direction of the blow- 
out. 

FUSES 

The test sheet should contain the catalogue number, ampere 
rating and dimensions of the fuse, also the style of box or holder 
in which the tests were made. 

Before starting the test, carefully inspect the fuses for defects, 
such as sharp bends, dents, burred holes, etc., discarding those 
that are not perfect, unless the test is being made to get an 
average curve on fuses from stock. 

Test to Determine Rating 

Connect a switch to the fuse box or holder, using a short- 
circuiting switch in multiple with both. If run off the shop 
circuit connect a water box in series. If run from the "booster," 
the current can be controlled from the booster field with a low 
resistance grid in series with the booster armature. 

With the series switch open, and the short-circuiting switch 
closed, adjust the current to the desired value, and hold as 
near constant as possible. Then close the series switch quickly 
and open the short-circuiting switch, and note the time by a stop 
watch it takes before the fuse blows. Fuses are rated at one- 
half the current at which they blow in thirty seconds. 

When a number of fuses are blown, the holder is likely to get 
very hot unless care is taken to cool it between tests. Ther- 
mometers should generally be placed on the fuse holder and the 
temperature kept below 75 deg. cent. 

Time-Current Curve 

To obtain time-current curves, fuses should be blown at 
current values which will blow the ribbons at periods varying 
from ten seconds to three minutes. 

369 



COUPLERS 

In train-control work, couplers are used to make temporary 
connections for the bus line, and control circuits between the 
cars of a train. Two parts are included in the complete coupling; 
the socket coupler, Type DA, and plug coupler, Type DC, which 
fits into the socket coupler. 

The contact terminals should be well fastened in the com- 
pound base, and the cover on the DA coupler should be held 
firmly closed by the spring. 

Couplers without cables are simply given a high-potential 
test, from the frame to each terminal, and between each terminal 
and the adjacent terminal. 

Sockets are placed at the ends of the car and cables run 
from them to the connection boxes in the car. When the socket 
is assembled with a cable, it is given the usual high potential 
test, and then each terminal is rung out with a lamp circuit to 
see that it is connected to the proper cable wire. 

CONTACTOR BOXES 

In the Type M or C control, instead of breaking the motor 
circuits in the controller, as is done in the K control, the con- 
troller operates a set of contactors assembled in a contactor 
box, which open and close the motor circuits. One contactor 
box is placed on each car, and the control circuits, besides 
being brought to the controllers of the car, are taken to couplers 
at either end of the car, from whence they can be connected by 
jumpers to other cars, and operated in multiple with them. 
The whole train is thus controlled from one controller. This 
control is manufactured either automatic or non-automatic. 

In non-automatic equipments, the motorman has full 
control of the acceleration of the car. In the automatic equip- 
ments, however, he does not control the resistance (accelera- 
tion) points. The automatic feature can readily be connected. 
One end of the cable is left open which can be afterwards con- 
nected to the connection boxes. The different wires are desig- 
nated by various colors. For the colors and numbers correspond- 
ing see the DS diagram. 

Inspection 

Each interlock should be carefully inspected to see that the 
rod is properly stamped, and that the disks agree with the 
Engineering Brief in regard to wipe and break. 

The terminal board and the terminals on all wires should be 
clearly and properly stamped and all wiring neatly done. The 
interlock rods should clear the back frame of the box by at least 
Y /i in. The name plate on each contactor and on the contactor 
box itself should be checked. 

Operation Test 

Each contactor box is connected to a controller and reverser, 
and operated so as to test all the control circuits. The main 
or motor circuits are rung out according to the DS diagram. 

370 



The operating voltage for each set of equipments should be 
obtained from Engineering instructions. The contactors should 
pick up and fully wipe on the minimum voltage, in the order 
specified. See that the arc is promptly ruptured on the inter- 
locks having magnetic blowouts. 

Potential Relay 

All automatic equipments having a potential relay should 
operate at a voltage higher than that at which the relay picks 
up. 

JUMPERS 

A jumper consists of two coupler plugs connected by a 
cable. It completes the circuits between cars. 

After the high-potential test, jumpers are "rung out" to 
see that the correct connections exist between the plugs as called 
for on the Engineering Notice. 

CIRCUIT BREAKERS 

There are several types of railway circuit breakers, the DB 
and MR representing the present standard. Most of the forms 
are fitted with a brush contact, auxiliary to the breaking finger 
contact, the latter being protected from the arc when opening by 
the contact fingers, which always open last. 

The AIR circuit breaker is closed manually by throwing 
the handle to the "on" position and can be tripped by throwing 
the handle to the "off" position, which gives a quick break open- 
ing. It is also arranged to trip out automatically on overloads. 

The DB circuit breakers are used for Type M control and 
are provided with solenoids for opening and closing. The coils 
are energized through a switch in the motorman's cab, the 
breakers themselves usually being under the car. 

Inspection 

All the cable terminal thimbles should be well fastened in the 
terminal blocks to prevent being lost in transportation. The 
arcing or secondary fingers should remain in contact when open- 
ing the circuit breaker, after the brush has opened contact by at 
least \i in. Both brushes and secondary fingers should make 
contact over their full width. All auxiliary switches on the cir- 
cuit breaker should be examined to see that they make good 
contact at the proper time. The copper shunts should be free 
from kinks or sharp bends. 

Calibration 

Each circuit breaker is calibrated for three tripping points. 
It is first tested for low tripping point, then for high point 
and finally for the intermediate point. It is left at the latter 
point, and the check nut is then set. Marks must be made 
designating the relative position of the cap of the calibrating 
spring for the different currents. 

Blow-Out Test 

Each circuit breaker is given a blow-out test in order to 
determine the direction of the arc. 

371 



RELAYS 

Railway relays can generally be classed under three heads: 
Current, potential and accelerating relays. 

Current Relays 

Current relays comprise all those which have their tripping 
coil in series with the circuit in which the current is to be con- 
trolled; the controlling circuits being wired through its disks 
or relays. 

Potential Relays 

Potential relays comprise all those having their operating 
coil shunt connected. These relays are used where a certain 
value of voltage is required for proper operation. Their func- 
tion is either to cut out resistance in control circuits, thus per- 
mitting lower voltage operation, or to transfer, or change control 
circuits. 

Accelerating Relays 

Accelerating relays are used with automatic control, their 
function being automatically to advance control connections. 

OPERATING TEST 

The relay should be able to break the specified amount of 
current on the contact studs, and if provided with a blow-out 
the arc should blow in the proper direction. 

The operating coil should operate the relay under the con- 
ditions specified in the Engineering instructions. The disks 
or arms should make good contact on the studs, and the wiring 
should be arranged in workmanlike fashion to prevent electrical 
or mechanical breakdowns in operation. 



372 



CHAPTER 23 

PROJECTORS 

Projectors are designed for operation from direct current 
circuits and it is necessary to provide motor-generator sets or 
mercury arc rectifiers where only alternating current supply is 
available. 




Fig. 162 
HAND CONTROL PROJECTOR 

The standard line of rheostats is designed with adjustments 
for line volts varying between 110 and 125 volts. When pro- 
jectors are operated in series or when one projector is operated 
from a line of greater than 125 volts potential, it is necessary to 
provide automatic cutouts with resistances equal to the resistance 
of the arc under normal conditions and rheostat capacity suffi- 
cient to take up the difference between the sum of the arc volt- 
ages and the line voltage. 

Inspection 

All projectors are inspected before the final test to see that the 
drum is balanced, that no bolts, screws, nuts, or cotter pins are 
missing, and that the rating on the name plate is correct. 

373 



Types of Control 

Hand — The hand control projector shown in Fig. 162 is 
controlled by handles on the rear of the drum and is provided 
with clamping devices for the horizontal and vertical planes. 




Fig. 163 
PILOT HOUSE CONTROL PROJECTOR 



Pilot House — The pilot house control shown in Fig. 163 
is operated from the inside of the pilot house by a controlling 
gear extending through the roof, the movement in both the hori- 
zontal and vertical planes being controlled by one handle. 

Rope Control — The rope control projector shown in Fig. 
164 is operated by means of cables connected to the controlling 
gear of the projector. As the movements in both the hori- 

374 



zontal and vertical planes are controlled by a single handle the 
controlling gear may be placed in the pilot house, on the bridge, 
or at any other convenient place. 

Electric Control — -The electric control is of three types. 
First, the direct armature control in which the entire current 
for the motors is carried through the controller cable, the con- 
tacts in the controller being arranged to start, stop and reverse 
both the elevating and training motors, and so connected that 
the beam follows the movement of the controller handle. This 
control is employed in the 13 and 18 inch sizes. 





Fig. 164 
ROPE CONTROL PROJECTOR 

Second, the rheostatic control in which the training and 
elevating motors are controlled from a distance through the con- 
troller cable, the controller being provided with resistances 
which give one or more speeds of training and elevating motors. 

Third, the synchronous control in which only the current 
required by the pilot motors is carried through the controller 
cable, the controller operating the pilot motors which in turn 
control the elevating and training motors. 

Adjustment 

A great deal of testing and adjusting of the electric control 
is done during the construction of the operating mechanism. 
For the synchronous control projectors, the pilot motors are 
connected and tested for polarity in accordance with Fig. 165, 
after which they are returned to the assembler for final connec- 
tion. The motor is then wired to a controller and if connected 
correctly the rotating field will take up 12 equidistant positions 
per revolution. After this test the pilot and training motors 
are assembled and wired, and thoroughly tested to insure the 
wiring being correct. When the projector is assembled the 
electric control is operated for some time to make sure that 

375 






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the connections are correct and that there are no mechanical 
faults in the training and elevating mechanism. Lamps are 
wired, adjusted and operated at the proper current and arc 
voltage, care being taken that the gap at the circuit breaker 
in the feeding magnet circuit is of the proper length, also that 
the screws limiting the motion of the pawls are properly set after 
which the feeding magnet armature spring may be adjusted so 
that the lamp will operate at its rated arc voltage. At the end 
of this test the lock nuts should be tightened and a general 
inspection of the mechanism made to see that everything is 
properly secured. 

With the lamp in position in the projector and in operation 
the position of the lamp should be adjusted by means of the 




Fig. 166 
MEASUREMENT OF FOCAL DISTANCE 



focusing screw so that the beam will appear to be composed of 
parallel rays. 

Mirrors 

Referring to Fig. 166, the mirror A is held facing an object 
B approximately 100 feet from the mirror and a piece of ground 
glass or white card C is then moved backward and forward in 
the focus. When the focus is reached the image of the object is 
very distinct. The distance from the card to the center of the 
reflecting surface of the mirror is the focal length. Mirrors are 
tested for regularity of curvature and grinding by placing 
them in front of a large white screen on which horizontal black 
lines are drawn. The lens of the camera is placed back of the 
screen and through a hole in the center and the reflection of the 
right lines is photographed. Fig. 167 shows a mirror in which 
the curvature of the reflecting surface and the grinding is correct. 
Fig. 168 shows a mirror with irregularities in the reflecting sur- 
face which can be distinctly seen in the photographic test. 

Rheostats 

A rheostat or ballast is connected in series with the arc when 
it is operated from a constant potential circuit. The object of 
this resistance is to prevent fluctuations of the arc current. 

377 



Fig. 167 
SHOWING CORRECT CURVATURE OF MIRROR 



378 




Fig. 168 
SHOWING IRREGULARITIES IN CURVATURE 



379 



Carbons 

One per cent of all projector carbons are tested. The points 
to be observed are as follows: 

The kind of arc obtained, whether quiet or noisy, steady or 
wandering; the amount of refuse left in the lamp after the car- 
bons have been consumed, and the amount which the carbons 
burn out of focus. 

The table on page 381 gives the sizes of carbons, etc., for 
standard apparatus. 

SIGNAL APPARATUS 
Keyboards 

Keyboards must be wired and every combination tried, care 
being taken to see that the proper lamps light and that the con- 
tact switch makes contact so that the lamps light simultaneously. 

An insulation test is made at 500 volts. The cables are 
connected to the keyboard and every combination gone through 
to see that the connections are correct. The connections 
to the receptacles should be inspected to see that there are no 
loose ends of wire to short-circuit or ground the receptacle. 

Trucklight Controllers 

Trucklight controllers are wired and tested to see that the 
proper lamps light and that the pulsator works correctly. 

Diving Lamps 

Diving lamps are tested under water, as specified in the 
Government specifications for the apparatus, to see that leakage 
does not occur. 



380 



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381 



Instructions contained in the following 
chapter must be followed by all men 
while working in the Transformer 
Testing Department at Pittsfield. 



383 



CHAPTER 24 

TRANSFORMER TESTS 

CONSTANT POTENTIAL TRANSFORMERS 

Tests 

Complete Tests consist of commercial tests and of normal 
and overload heat runs. 

Commercial Tests consist of cold resistance, polarity, 
ratio and checking taps, impedance, core loss, exciting current 
and insulation tests. These are applied to all transformers, 
except for the resistance test which is often omitted on duplicate 
transformers of small capacity. 

Normal Load Heat Run consists of operating the trans- 
former at normal load until it shows constant temperature. 

Overload Heat Run consists of operating the transformer 
until it has reached normal load temperature and then applying 
the required overload for the specified time. 

Efficiency is calculated from the core loss and the resistance 
at 25 deg. cent. 

Regulation is calculated from the impedance and the resist- 
ance at 25 deg. cent. 

Insulation Tests are: (1) the high potential test, which 
consists of applying high voltage between windings and from 
windings to ground; (2) the induced voltage test, which consists 
of operating the transformer at considerably more than normal 
voltage for a short time. 

Types of Transformers 

For purposes of test, constant potential transformers may 
be conveniently divided into four classes, depending upon the 
method of cooling as follows: 

Natural draft 

Air blast 

Oil immersed self cooled 

Oil immersed water cooled. 

Natural draft transformers have the core and coils exposed 
directly to the air, and depend entirely upon the natural cir- 
culation of the air for their cooling. They are built only in small 
sizes and low voltages, seldom over 25 kv-a. or 1000 volts. 

Air blast transformers depend upon a forced circulation of 
air over the surface of core and coils to carry away the heat. 
They may be built for large capacities, but the voltage rarely 
exceeds 30,000 because of the difficulty of insulating them prop- 
erly. 

Self cooled oil immersed transformers have the core and coils 
immersed in a tank of oil. This tank is usually made of cast or 

384 



sheet iron, and is quite often corrugated so as to increase the 
surface available for dissipating the heat generated in the core 
and coils. Sometimes external tubes or radiators through which 
the oil circulates are used for this same purpose. 

"Water cooled oil immersed transformers depend on the cir- 
culation of water through a coil of iron, brass or copper, placed 
in the top of the tank to carry away the heat from the oil. The 
tank, which is usually made of steel plate dissipates only a small 
portion of the heat. This type is used for the largest capacities 
and is suitable for any voltage. 

The method of cooling affects principally the insulation test 
and the heat run, since oil immersed transformers depend on 
the oil for insulation, as well as for cooling. It is necessary 
that they be filled with oil of the proper quality when more than 
a small percentage of their normal voltage is applied to or 
induced in them. During the heat run, transformers must be 
filled with oil if they are of the oil immersed type, and must be 
subjected to the cooling conditions for which they are designed. 

Order of Tests 

The order of tests is to a great extent left to the discretion 
of the man making them. The cold resistance must be measured 
before the transformer has been heated up by any other tests, 
care being exercised to obtain the correct temperature of the 
windings. The heat run, high potential and induced voltage 
tests should be made last and in the order named, except that 
for transformers of 100 kv-a. or less the induced voltage may be 
placed before the high potential test. 

Preparation for Tests 

Information from the Engineering Department, regarding 
guarantees, rating, operating conditions, etc., is furnished to the 
testing department by means of test data cards, Engineering 
Notices, DS sketches, and specifications. On power trans- 
formers, which include all sizes of over 100 kv-a. the test 
records are prepared in advance by the calculators in the Test- 
ing Department so that it is not necessary for the man making 
the tests to refer to any instructions from the Engineering 
Department. The test record then shows the guarantees, the 
special requirements and sketches of windings. On standard 
lighting transformers full information is given on the test data 
card. On special transformers of small sizes the test data card 
is sometimes supplemented by an Engineering Notice and 
always by the DS sketch. Reference should be made to all these 
before starting the tests. 

The transformers must be properly placed in position for 
test, especially if there is to be a heat run. Great care must be 
exercised to see that air blast transformers are properly sup- 
ported above the pit, as otherwise they may fall and injure 
persons stationed under them. No opening should be left 
through which air can escape and influence the readings of the 

385 



thermometers on the iron. Large transformers, especially 
those of self cooled types, should be so located as to allow free 
air circulation between units during the heat run. The distance 
between self cooled transformers of over 100 kv-a. capacity 
should be at least 2 ft. and if possible, a greater distance. Such 
transformers should always be placed not less than 12 in. from 
the walls of the testing pit. Idle units used in checking heat run 
temperatures should be located at least 4 ft. from the hot units 
or other sources of heat. 

Cold Resistance 

The cold resistance measurements are used for two pur- 
poses; first — for calculation of copper loss and consequently for 
efficiencies; and second — for the determination of the tempera- 
ture rise of the windings. 

The drop of potential method should be employed unless the 
rated current of the windings is less than 1 ampere, in which 
case the Wheatstone bridge may be used. The current used 
should not be more than 15 per cent of the rated current of the 
winding, as a larger value is liable to cause heating, making it 
impossible to obtain accurate values of the temperature of the 
windings. The voltmeter leads should be attached to the ter- 
minals of the transformer separately from the leads carrying the 
current, so as to avoid including the drop in voltage due to the 
temporary connections. In measuring cold resistance, a spot 
on which to hold the voltmeter leads should be cleaned with 
sandpaper. 

Resistance of the full series winding should always be 
measured. In case the heat run is to be made on a tap or on a 
multiple connection the cold resistance of such connection should 
also be measured. 

It is important that the temperature of the windings at the 
time the cold resistance is measured be determined accurately, 
especially where this resistance is to be used for the calculation 
of temperature rise. It is advisable therefore to take several 
readings of resistance and temperature at half hourly intervals, 
the thermometer being placed on or very near the coils. 

The resistance of each winding at 25 deg cent, should be 
calculated and noted on the test sheet. The method of calculat- 
ing the rise in temperature by increase of resistance is 
explained under the subject of heat runs on page 399. 

Polarity 

The polarity test gives the only means of readily determining 
the connections required for transformers in banks, for instance, 
several transformers in parallel. General Electric Company 
transformers always have the same polarity, except in some 
special cases where the customer requests that it be reversed. 
There are three methods of making the test, the most convenient 
one being used in each case. 

(1) When a standard transformer of the same ratio as the 
one under test is available, the polarity and ratio tests may be 
combined. 

386 



The high voltage winding of the transformer under test should 
be connected in multiple with the high voltage winding of the 
standard transformer and the low voltage winding of the 
transformer under test should be connected in multiple with the 
low voltage winding of the standard transformer. One winding 
(usually the high voltage) should be excited while a voltmeter 
is placed between the two low voltage windings to indicate 
the difference in voltage. If there is no difference in voltage, 
the polarity and ratio are both correct. If there is a small 
difference the polarity is correct, but the ratio is not. If the 
difference in voltage is great the polarity is probably reversed. 
Further tests should be made to determine whether this is true. 

(2) The polarity may be determined at the same time as the 
resistance by making use of direct current as follows: 

With direct current passing through one winding, usually 
the high voltage, connect a high voltage voltmeter across the 
terminals so as to obtain a positive deflection. Then transfer 
the two voltmeter leads directly across the transformer, the 
lead from the right-hand high voltage being placed on the right- 
hand low voltage (facing the high voltage side), while the lead 
from the left-hand high voltage is placed on the left-hand low 
voltage terminal. Then break the current in the first winding, 
thus inducing momentarily a voltage in the other. If a positive 
kick of the voltmeter needle is produced the polarity is correct 
according to the standard General Electric Company practice. 
In case the polarity is indicated on the DS sketch by means of 
positive and negative signs, it should be checked in the manner 
explained above, except that the voltmeter lead resting on the 
high voltage terminal bearing a given sign (positive or nega- 
tive) should be moved to the low voltage terminal bearing the 
same sign. 

(3) If neither a standard transformer nor a source of direct 
current is available, the polarity may be determined by ratio as 
follows : 

While facing the high voltage side connect the right-hand 
high voltage to the right-hand low voltage terminal. Excite 
the high voltage winding and read the voltage induced between 
the left-hand high voltage and the left-hand low voltage ter- 
minals. If this is greater than the voltage impressed on the high 
voltage winding the polarity is correct according to standard 
General Electric Company practice. In case the DS sketch 
indicates the polarity the test should be made in the same way, 
except that the positive high voltage terminal should be con- 
nected to the positive low voltage terminal and the voltage read 
between the two negatively marked terminals. 

Determination of polarity on three-phase transformers 
requires much care. The accompanying diagrams allow a 
comparison to be made of the various standard connections. 

Figs. 169 to 174 show standard connections for three-phase 
shell type transformers and Figs. 175 to 180 for three-phase core 
type transformers. It is understood that the leads are brought 
out as shown in these standard sketches, unless distinctly specified 

387 



otherwise by the DS sketch or by special instructions. It is 
best to use direct current for such tests, each phase being checked 
separately. 

In checking polarity of delta-delta, delta- Y, Y- Y or F-delta 
connections, impress direct current from X to Y on the high 



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Figs. 169 to 174 
STANDARD THREE-PHASE CONNECTIONS, THREE- 
PHASE SHELL TYPE TRANSFORMER 

Notes. — In effect, high voltage and low voltage windings are wound in 
opposite directions. 

Diagrams should be read facing low voltage side of transformer. 



voltage, place the voltmeter across X to Y so as to obtain a 
positive deflection; then move the voltmeter lead on X high 
voltage over to X low voltage and the one on Y high voltage to 
Y low voltage. Break the circuit and note the deflection of the 
voltmeter. If it is positive the polarity is correct. The other 
two phases must then be checked in the same way. 

In checking F-diametrical connections (Figs. 173 and 179) 
excite X to Y for checking phase 1 ; also for phase 2. For phase 

388 



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Figs. 175 to 180 
STANDARD THREE-PHASE CONNECTIONS, THREE- 
PHASE CORE TYPE TRANSFORMERS 

Notes. — High voltage and low voltage winding wound in opposite direc- 

Xumbers 1, 2, 3 on diagrams refer to corresponding phases. 

Fig. 177a is for transformers having high voltage winding 5300 volts or less. 

Fig. 177b is for transformers having high voltage winding over 5300 volts. 

389 



1 transfer the lead from X high voltage to X low voltage and 
from Y high voltage to X' low voltage. For phase 2 transfer 
from Y high voltage to Y low voltage and from X high voltage 
to Y' low voltage. For phase 3 excite Z to X, then transfer 
from Z high voltage to Z low voltage and from X high voltage 
to Z' low voltage. 

In shell type delta-diametrical (Fig. 174), proceed as follows: 
For the left-hand phase excite X to Y high voltage and transfer 
from Y high voltage to X low voltage, and from X high voltage 
to X' low voltage. For the middle phase excite X to Z and 
transfer from X high voltage to Y low voltage and from Z high 
voltage to Y' low voltage. For right-hand phase excite Y to Z, 
transfer from Z high voltage to Z low voltage and from Y to Z' 
low voltage. 

For core type delta-diametrical (Fig. 180) proceed as follows: 
For phase 1, excite X to Z, transferring X high voltage to X low 
voltage and from Z high voltage to X' low voltage. For phase 

2 excite X to Y, transfer from Y high voltage to Y low voltage 
and from X to Y' low voltage. For phase 3 excite Z to Y, 
transferring from Z high voltage to Z low voltage and from Y 
high voltage to Z' low voltage. 

Phase Rotation 

In addition to the polarity test it is necessary to check the 
phase rotation on all three-phase and six-phase transformers 
except on such as are run in parallel with one on which the test 
has already been made. 

The phase rotation meter should be connected to the high 
voltage side of the transformer and a relatively small voltage 
applied. This voltage should be sufficient to cause rotation of 
the meter but should not exceed 550 volts. The direction of 
rotation should be noted. Then the leads from the meter should 
be transferred straight across the transformer to the low voltage 
terminals. The transformer should again be excited with voltage 
sufficient to cause the meter to rotate end the direction of rota- 
tion should be noted. When the direction is the same on the low 
voltage as on the high voltage side, the result should be marked 
on the test sheet as "Standard." When it is opposite on the two 
sides, attention should be called to that fact on the test sheet. 

Six-phase transformers having double delta connections 
must have the rotation checked on each delta. 

Transformers having diametrical connection with the middle 
points of each phase brought out should have these points joined 
after which phase rotation should be checked by selecting ter- 
minals which will give two Y-connections. In addition to the 
test with the meter these transformers should have the neutrals 
connected together while the six voltages are read between each 
pair of consecutively numbered leads. These should all be of 
equal value and also should be equal to the voltage from any 
one of them to the neutral point. When the neutral points are 
not brought out a temporary delta connection should be made 
for the phase rotation test. 

390 



Ratio 

The ratio of a transformer is the ratio of voltage of the high 
voltage winding to the low voltage winding. The required 
voltages are given in the rating and are shown on the DS sketch. 
The ratio should be measured on at least one of each group of 
similar transformers and compared with the ratio shown by the 
DS sketch. The ratio of all other transformers in the group 
should be checked by running each in parallel with the one on 
which the ratio has been measured. 

The transformer should be operated at normal frequency or 
higher and at normal voltage or lower during the ratio test. An 
exception to this rule is made for transformers having capacities 
of 500 watts or less and with exciting current of more than 10 
per cent. These should be tested at normal voltage and fre- 
quency. 

Where possible, it is best to make a ratio test by comparing 
the transformer with a standard of exactly the same ratio. The 
two should be connected in parallel on both sides and the high 
voltage winding excited while a voltmeter is used to read the 
difference in voltage between the two low voltage windings. 

When the above method is not applicable, two voltmeters 
should be used, one to read the low and the other to read the 
high voltage, the latter being stepped down through a potential 
transformer when necessary. Where voltages and scales will 
permit, the instruments should be interchanged between read- 
ings so as to eliminate errors. It is best to take at least two 
sets of readings, calculating the ratio from each and considering 
the average as the correct value. 

The parallel run should be made at normal frequency and 
normal voltage, the voltage being applied usually to the low 
voltage winding. A test for circulating current between the 
two high voltage windings should be made by closing and opening 
the circuit. If a spark is observed a further test should be made 
by measuring the amperes circulating through the high tension 
winding and by measuring the difference in voltage on open 
circuit. If no spark appears on the first test, it is best to make 
sure of the presence of voltage in the winding by touching the 
free high voltage terminal to the case (at reduced voltage). 
If the circulating current is more than 5 per cent of the rated 
current of the winding, attention should be called to the fact 
on the test sheet. 

On three-phase transformers it is preferable to use single- 
phase power and to measure the ratio of each phase separately. 
This is not possible when the neutral point of a Y-connection is 
not brought out. In such cases three-phase power must be used. 

On Y- diametrical transformers where the neutral point is 
not brought out, three-phase excitation must be used. Any 
inequality in the magnetizing characteristics of the three phases 
will result in distortion of the neutral, thereby causing unequal 
phase voltages. When such an inequality is found the diametric 
connection should be changed to a Y-connection and the phase 
voltages measured. If these are equal and of the proper value, 

391 



i.e., V3 times the diametric voltage, the ratio may be con- 
sidered as being correct. If the voltages are still unbalanced, 
however, the transformer should be returned to the Assembly 
Department so that the neutral point can be brought out. 
It should then be tested single-phase and if -the phase ratios 
are correct the transformer may be passed. The Y-connection 
may be made from the diametrical by referring to the standard 
connection diagrams previously referred to under polarity test. 
A variation of more than Y% of 1 per cent above or below 
the value shown on the DS sketch or connection label on stand- 
ard lighting transformers should be called to the attention of the 
Engineering Department. On other transformers the allowable 
variation is 1 per cent. 

Wattmeter Ammeter 




Primary Secondary 



Fig. 181 
CONNECTIONS FOR IMPEDANCE TEST 



Checking Taps 

Nearly all transformers are provided with taps in one or both 
windings, so that a slight change in ratio or a low voltage for 
starting may be obtained. These tap voltages should be checked 
to determine whether they agree in voltage and in position with 
the DS sketch. This test may be made either by means of the 
"two voltmeter method" or by running the transformer in 
parallel with a standard transformer or with one on which the 
test has already been made. When two voltmeters are used, it 
is best to apply a low voltage to the full winding, then read the 
voltage from the terminals to the first tap, then between succes- 
sive taps of the same winding. Care should be taken in handling 
the voltmeter connected to the tap, because, although the voltage 
reading is low, the circuit to which it is connected may be 
several thousand volts above ground. If the opposite end of 
the circuit be grounded a severe shock may be obtained from 
the meter. 

On windings having low voltage taps at the ends it is some- 
times necessary to check their location by checking the polarity 
of each section of the winding. If the polarity of each is correct 
the taps are properly brought out. 

392 



Impedance 

The impedance of a transformer is measured by short- 
circuiting one of the windings and impressing an alternating 
e.m.f. on the other windings and taking simultaneous readings 
of amperes, volts, watts, and frequency. The impedance of 
transformers should be carefully measured for the following 
reasons: Transformers operating in multiple divide the load 
inversely as their impedance voltages; i.e., the one having the 
higher impedance will take the smaller part of the load and vice 
versa. When transformers of different types are operated in 
multiple, the impedance of one transformer must sometimes be 
increased by putting a reactive coil in the secondary circuit, and 
adjusting until the desired impedance is obtained. 

Impedance tests show whether a given arrangement of 
coils is satisfactory or not. If the arrangement is not satis- 
factory, excessive magnetic leakage will take place and high 
impedance voltage result. The impedance watts will also be 
high, due to excessive eddy current loss in the copper. Since 
regulation depends upon impedance to a great extent, a low 
impedance is very necessary for close regulation. 

The impedance voltage of lighting transformers varies from 
about 1 to 4 per cent while that of power transformers is usually 
from about 4 to 8 per cent. Transformers for operating syn- 
chronous converters are often provided with magnetic shunts in 
order to obtain high impedance, that is from 12 to 20 per cent. 
The impedance watts do not as a rule exceed 1 to 1 Y2 per cent 
of the total capacity of the transformer, although they are 
higher than the calculated I 2 R on account of the eddy current 
losses in the copper. 

The following method should be used in making the test: 
Place a thermometer on or very near the coil so as to obtain the 
exact temperature. Make a good short-circuit on one winding, 
using as short a cable as possible and one of ample cross section 
so that no appreciable losses will occur. Make the connections 
shown in Fig. 181. Adjust the current with the pressure circuits 
of the voltmeter and wattmeter open, then close the pressure 
circuits and take the reading of volts and watts. See Fig. 181. 
The watts should be corrected for the losses in the voltmeter, 
wattmeter and instrument transformers (if any are used). 

In measuring the impedance of three-phase transformers, 
the two wattmeter method should be used, a single set of instru- 
ments being transferred from one phase to the other by switches. 
The current should be adjusted so that the average value in the 
three lines is equal to the normal rated current. 

If the measured impedance watts exceed the calculated PR 
watts by more than 15 per cent, attention should be called to 
that fact on the test sheet. 

Core Loss and Exciting Current 

When the transformer is connected to a source of alternating 
e.m.f. a loss of energy takes place in the iron due to the cyclic 
reversals of the magnetic flux. This loss of energy is known as 

393 



core loss. Its value depends on the wave form of the impressed 
voltage as well as upon the value of that voltage. A peaked 
wave gives lower losses and a flat wave gives higher losses than 
a true sine wave. The core loss energy should therefore pref- 
erably be taken from a sine wave alternator operated at about 
its normal excitation. 

The core loss test is similar to the impedance test except 
that the voltage is applied to one winding, all others being open- 
circuited. It is usually preferable to apply voltage to the low 
voltage winding so as to avoid reading meters in high potential 
circuits. Care should be taken to see that the high tension 
cables are located so that no one can come in contact with them 



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Fig. 182 
CONNECTIONS FOR HEAT RUN 




and so that there is no danger of a short-circuit. During the 
test it is best to have the windings connected according to some 
one of the connections shown on the DS sketch. It is par- 
ticularly necessary to avoid leaving windings open at points 
where they would not be left open under operating conditions 
as it is sometimes possible to obtain excessive stresses between 
points of the same winding by leaving such connections open. 

The connection of instruments in measuring core loss should 
be the same as in the impedance test and the reading should be 
taken in the same way. In measuring the loss of three-phase 
transformers it is advisable to take three entirely separate sets 
of readings by the two wattmeter method, each of the three 
lines being used in succession as the neutral. The average 
value of the three sets of readings should be recorded as the 
true core loss. 

As alternators with perfect sine waves are very difficult to 
obtain, it is customary to correct the measured loss to a sine 
wave basis, by means of the core loss correction outfit. This 
outfit consists of a single winding on a small core, the sine wave 
loss of which has been carefully determined over a wide range of 
voltage. The outfit should be connected to the same source of 
power as the transformer under test, after which normal voltage 
should be applied to the latter. The loss in the standard core 
and the voltage across its terminals should be measured at the 

394 



same time as that of the transformer under test. The sine 
wave loss of the standard core at the same voltage should then 
be determined from the calibration curve. The ratio of the 
measured loss of the standard core to the reading taken from the 
calibration curve should be used to reduce the measured loss 
of the transformer under test to a sine wave basis. 

The exciting current may be corrected for wave shape by- 
carrying the test a little further. After the core loss correction 
has been determined, the voltage should be raised until the 
measured loss is equal to the corrected loss. The exciting cur- 
rent read at this voltage is approximately the true sine wave 
value. 



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Fig. 183 
CONNECTIONS FOR HEAT RUN 



Heat Run 

The heat test may be conducted in several ways, all of which 
are intended to approximate as nearly as possible the actual 
operating conditions. The run with actual load may be made 
by using lamps, water rheostats or choke coils, but as this is 
very expensive except for small devices, some form of motor- 
generator method is usually employed. 

Fig. 182 shows the connections for testing two transformers 
by the motor-generator method. The secondaries of the two 
are connected in multiple and are then connected to an alter- 
nator which supplies the core loss and exciting current. The 
primaries are connected in series and opposing each other. If 
the transformers have the same ratio, the voltage from A to B 
will be zero. 

The secondary of an auxiliary transformer D is connected 
in series with the primaries and an alternator E is used to 

395 



supply the copper losses through this transformer D. The 
same method may be used for any even number of transformers, 
but it is not advisable to connect more than two high voltage 
units in this way, or more than six or eight units of any volt- 
age. The arrows show the direction of the load currents. 

Fig. 183 shows the connections for a heat run on three single- 
phase transformers. This method may also be used for one 
three-phase transformer when the windings can be connected 
in delta on each side. The three-phase alternator is used to 



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Fig. 184 
CONNECTIONS FOR HEAT RUN, THREE-PHASE 



supply the core loss and exciting current. One of the deltas is 
opened and sufficient single-phase voltage is impressed to cause 
full load current to flow. The current circulates within the 
deltas and is entirely independent of the three-phase voltage 
impressed by the core loss alternator. 

Fig. 184 shows the connections for a heat run on two three- 
phase transformers in which three-phase current is used to 
supply the copper losses and three-phase voltage for the core 
loss. The auxiliary transformers A, A', A" may or may not be 
used depending on whether the voltage of the alternator B 
supplying the core loss is of the proper value or not. Auxiliary 

396 



transformers, B, B' and B" are used as series transformers to 
supply the impedance voltage. 

Fig. 185 shows connections for the heat run on two inter- 
changeable single-phase units designed for operation on "T" 
connected two-phase-three-phase circuits. It is the common 
practice to make such units interchangeable, each having the 
50 per cent and 86.6 per cent taps so that either may be used 
as the main or the teaser. In actual operation the one used as 
the main has a somewhat heavier load than the teaser. How- 
ever, since either may be used as a main, the heat run should 
be made with the heavier load. The connections shown in Fig. 
182 should not be used as with such a connection and with normal 
current in the winding for use on the two-phase circuit, the cur- 
rent in the three-phase side will be only 86.6 per cent of that 






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Fig. 185 
CONNECTIONS FOR HEAT RUN ON SINGLE-PHASE UNITS 
FOR OPERATION ON T-CONNECTED TWO-PHASE- 
THREE-PHASE CIRCUITS 



flowing under operating conditions. It is necessary to use con- 
nections shown in Fig. 185. The core loss is supplied in the 
regular manner and the normal current of the two-phase winding 
is supplied from alternator E through transformer D. An 
additional current is supplied from alternator / through trans- 
former H to the middle points F and G of the two three-phase 
windings. Since F and G are the middle points, no voltage is 
induced between them by the core loss alternator, and further- 
more, the current supplied by alternator / flowing in opposite 
directions in the two halves has no resultant effect upon the 
two-phase windings. The current from alternator J must 
be of such value as to produce a resultant current in the three- 
phase winding 15.5 per cent greater than that produced by 
alternator E alone. The frequency of alternator / must be 
different from that of alternator E so that the effect of the two 
currents in the three-phase winding will be equivalent to that 
obtained by adding them in quadrature. 

The methods described above are the ones most commonly 
used, but it is often necessary to modify them so as to fit special 
conditions. 

It will be noted that no provision has been made for making 
a heat run on a single transformer, except for such three-phase 

397 



units as can be connected delta on each side. As a rule such 
units cannot be given a normal load run without the use of 
actual load. However, there are other methods which may be 
used in special cases. Sometimes, it is possible to use a set 
consisting of two alternators on the same shaft, the transformer 
being connected between the two and the load current being 
adjusted by varying the alternator fields. Another method 
is applicable in case each winding is divided into two equal 
parts. The run may then be made by paralleling each winding 
separately and supplying core loss to one side and forcing the 
load current through each winding separately. In addition to 
the above, there are some compromise runs which approximate 
the load condition. One method of making a compromise run 
is by supplying double the normal core loss over a short period 
and then supplying double copper loss for an equal length of 
time, this cycle of operation being repeated until constant 
temperature conditions are reached. 

In connecting the transformers under test for the heat run, 
it is best to use the series connection of each winding, as this 
connection is preferable for resistance measurements. Care 
should be taken to see that the alternators and auxiliary trans- 
formers are of sufficient capacity to carry the normal load and 
the overload. In calculating the current necessary to supply 
the core losses, take the sum of the exciting currents of the trans- 
formers. To calculate the voltage required to supply the load 
current add together the impedance voltages of the transformers. 
Shop transformers should always be interposed between the 
loading alternator and the transformers under test, so as to 
avoid having high potentials on the switchboard and prevent 
breaking down the insulation of the alternator. 

Thermometers should be placed on air blast transformers, so 
as to obtain the temperatures of the air at intake of blower, 
air from primary coils, air from secondary coils, air from core 
at top and bottom and temperature of core at top and bot- 
tom. In placing thermometers on three-phase units, each phase 
should have as many thermometers as are ordinarily used on a 
single-phase transformer. On water cooled transformers, the 
temperature of the ingoing water, outgoing water, top oil, top 
of tank near oil level and bottom of tank should be determined. 
On self cooled oil immersed units, the temperature of top oil, 
top of tank near oil level and bottom of tank should be deter- 
mined. It is best to avoid changing the position of thermometers 
when taking readings. At the end of the run, especially in the 
case of air blast transformers, the thermometers on the core and 
coils should be carefully watched until the temperatures begin 
to fall. The maximum values should be recorded. 

When three or more transformers are available for the heat 
run, it is advisable to use one of them as a base for determining 
temperature rise. The resistance and temperature of this 
transformer should be carefully measured in comparison with 
that of the other units before the heat run is started. During 
the run, it should be screened from the heat given out by the 

398 



other units but should be subjected to the same cooling medium. 
That is, if it is an air blast unit, air should be forced through it; if 
a water cooled unit, water should be forced through its cooling 
coil; and if a self cooled type, it should be subjected to the same 
surrounding air conditions as the ones on the heat test. During 
the run, its temperature should be noted at the same time as 
that of the hot units, these values being used as base or reference 
temperatures. At the end of the run, the resistance of the hot 
and the "idle" units should be measured. The temperature rise 
is calculated from these final readings, a correction being made 
for any difference in the two initial resistances by multiplying 
the final resistance of the idle unit by the ratio of the initial 
resistance of the loaded unit to the idle unit. If an "idle" unit is 
not available, the reference temperatures should be as follows: 
On air blast transformers it should be the ingoing air; on water 
cooled units, the ingoing water temperature should' be used, and 
on self cooled transformers, the surrounding air temperature 
should be considered as the base. 

It is customary to overload self cooled transformers at the 
start of the heat run, so as to bring them up to operating tem- 
perature quickly. Air blast transformers are usually brought 
up to temperature on normal load, but without the use of the 
cooling agent. Water cooled units may be brought up on normal 
load, or slight overload without having water passing through the 
coils. 

As soon as approximately normal operating temperatures 
have been reached, the load is reduced to normal and the water 
started on the water cooled units or the air on the air blast. On 
water cooled transformers, the temperature of ingoing water 
should be adjusted to be approximately the same value as the 
room temperature at the start of the run. This value, when 
once decided upon should, however, be held throughout the 
run. The quantity of water should be adjusted so as to give a 
rise of exactly 10 deg. cent, in passing through the transformers. 
On air blast transformers, the air should be adjusted to the 
required pressure and both dampers should be left wide open. 
The quantity of air should be measured at the start of the run, 
and the quantity of water each hour during the run. 

The heat run should be continued until the rise of temperature 
is constant within one degree in three hours, this rise being deter- 
mined by means of thermometers. The load should then . be 
removed and resistances of hot and "idle" units measured. 
If the results do not seem to be consistent, the load should be 
replaced and the run continued until rises are again constant, 
after which a second set of resistance readings should be taken. 

The rise by resistance is calculated as follows: 

R h-Ro 
0.0042 Ro 

where Rh =h.ot resistance. 

Ro = resistance at 0° cent. «, 

/#=hot temperature of winding. 
399 



The following variation of the formula is found to be service- 
able for slide rule calculations: 

Rh 238 +tH 

Rc~238+tc 
where Re = the cold resistance of the winding.. 

tc = temperature corresponding to this cold resistance. 

During the heat run the temperature of the hottest part of 
a transformer should not be allowed to exceed 100 deg. cent, 
unless specific instructions to the contrary have been received 
from the Engineering Department. Where terminals carrying 
more than 1000 amperes are used, the temperature of each should 
be measured at the end of the heat run. 

High Potential 

The application of a high potential to the insulation of a 
transformer is the only method of determining whether the 
dielectric strength is sufficient for continuous operation. Me- 
chanical examination amounts to little and measurement of insu- 
lation resistance is equally valueless, since insulation may show 
high resistance when measured by voltmeter with low voltage, 
but offer comparatively little resistance to the passage of high 
tension current. The voltage of the insulation test depends 
upon the voltage for which the windings are designed, and upon 
the conditions under which the transformer is to operate. This 
voltage is always specified on the Standing Instructions or 
test data card. As a general rule, the voltage is double the 
operating voltage of the winding with a minimum test voltage 
of 10,000 for the high voltage and 4000 for the low voltage wind- 
ing. The duration of the tests is always one minute, unless 
otherwise specified. 

In testing from the high voltage winding to core or to low 
voltage winding, the low voltage winding should always be 
grounded to the core for the following reasons: In testing 
between one winding and the core, a potential stress is induced 
between the core and the other winding, which may be much 
greater than the stress to which the insulation is subjected under 
normal operation and greater, therefore, than it is designed to 
withstand. In testing between the high voltage winding and 
the core the induced potential between the low voltage winding 
and core may be several thousand volts, and the low voltage 
winding may thus be broken down by an insulation test applied 
to the high voltage winding under conditions which would 
not exist in normal operation. During the test all leads on the 
same winding must be connected together. If only one terminal 
of a winding is connected to the testing transformer, the strain 
may vary throughout the winding and at some point 
may even be greater than at the terminal at which the voltage 
is applied. 

The charging current of a transformer varies with its size 
and design. This current may be measured by means of an 
ammeter placed in the low voltage circuit of the testing trans- 

400 



former. It will increase as the voltage applied to the insulation 
is increased. Inability to obtain the desired potential across the 
insulation may be due to large electrostatic capacity, or to the 
inability of the testing transformer to supply large capacity 
current at the voltage desired. 

In making the insulation test, it is essential that the voltage 
be brought up gradually. 



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Fig. 186 
SPARK GAP CURVE 



The usual ways of controlling the voltage are as follows: 

1st. By means of a resistance in series with the low voltage 
side of the testing transformer. Another resistance of such 
magnitude as to allow a flow of current at least five times the 
exciting current should be connected in multiple with the low 
voltage side, so as to maintain a smooth wave shape under all 
conditions. 

2nd. By means of an induction regulator on the low volt- 
age side of the testing transformer. 

3rd. By variation of the strength of the generator field. 

401 



The first method is not well suited to very high potential 
tests on account of the large amount of resistance required. 
The second and third methods are, however, suitable for any 
voltage. 

In applying the test voltage, it should be started at less than 
one quarter of the final value, should then be brought up during 
30 seconds to the full value and after having been held the 
specified length of time should be reduced during about 15 
seconds to less than one-quarter of its maximum value, after 
which the circuit may be opened. 

The spark gap should be as near as possible to the trans- 
former under test and on tests of more than 15,000 volts it 
should never be more than 20 feet away. Resistances should 
always be placed in series with this gap, but never between the 
testing transformer and the one under test. The value of the 
resistances placed in series with the gap should be such as to 
limit the current from }/i to 2 amperes in case of a discharge 
across the gap. This will require from 4 ohms to 3^2 ohm per 
volt, 

For tests of 10,000 volts or less, it is usually the practice 
to depend upon the ratio of the testing transformer in determin- 
ing the voltage that is to measure the voltage on the low voltage 
side, a spark gap being placed across to the high voltage side 
and being set at 10 per cent above the required voltage as a 
safety valve. For tests from about 10,000 to 50,000 volts, 
the gap should be set in accordance with the curve of arcing 
distance shown. (See Fig. 186.) The voltage should be raised 
slowly until the gap breaks, at which time the voltmeter reading 
should be noted. The voltage should then be reduced to zero, 
and the spark gap setting increased to 10 per cent above its 
former value. The voltage should then be brought up until 
the voltmeter reads the same value, this voltage being held 
for the specified length of time. For tests above 50,000 volts, 
it is not advisable to cause the spark gap to break with the 
full voltage on the transformer under test. For such tests, 
therefore, the gap is first set for the desired voltage, while 
the transformer under test is entirely disconnected. The 
gap is then broken and the voltmeter reading noted. Then the 
gap is set for % of the required voltage and the voltmeter read- 
ing obtained for the breaking of this gap. The transformer under 
test is then connected and the gap broken at the setting for % 
voltage. The voltmeter reading obtained with this last setting 
is then multiplied by the ratio of the readings for full and for % 
voltage with the transformer disconnected and this calculated 
voltage is held by voltmeter for the actual test, the spark gap 
being set at 15 per cent above this voltage during the test. 

The presence of moisture in the coils and insulation lowers 
the dielectric strength to such an extent that it is general practice 
to dry carefully all high voltage transformers before they are 
filled with oil. The drying-out run should ordinarily be made 
on all transformers having test voltages above 100,000 volts, 
and upon any transformer having test above 15,000 volts if it 

402 



has been standing in the factory for more than two or three 
weeks before test. The drying is ordinarily done by forcing 
a blast of air at about 80 deg. cent, through the transformer 
and this continued until the insulation resistance measured by 
the megger shows practically constant values. 

Transformers having high potential test voltages above 
13,200 volts are filled with oil for the test. Care should be 
taken to see that the oil itself is of sufficient dielectric strength. 
Xo oil having strength of less than 20,000 volts between half 
inch disks 0.2 in. apart, should be used during the high potential 
tests. When the test voltage is higher, the strength of the oil 
should be correspondingly greater. For tests above 100,000 
volts, the oil should show a dielectric strength of at least 40,000 
volts. 

As the high potential test is made after the heat run, the oil 
has had an opportunity to free itself from air bubbles and to 
penetrate to every part of the transformer. In some cases, 
however, especially when the oil does not meet the requirements 
of dielectric strength, it is necessary to replace it before the high 
potential test. In such cases the transformer should be allowed 
to stand for some time before the test is applied. This period 
should be at least one hour for voltages of 50,000 and less, and 
at least 6 hours when the voltage is above 50,000. 

Induced Voltage 

Induced voltage is applied to transformers in order to test 
the insulation between turns and between sections of the wind- 
ings. The usual value of this test is twice normal voltage 
induced for a period of one mimvte, followed by one and one- 
half times normal voltage for five minutes. Low voltage trans- 
formers (5000 volts or less), usually have three times normal 
voltage applied for one minute. 

The source of power should have an approximate sine wave 
and a frequency such that the exciting current will not exceed 
150 per cent of the rated load current of the excited winding. 
It is common practice to use a frequency of 200 cycles for 25 
and 60 cycle transformers. The voltage may be controlled by 
any of the methods described for the high potential test. The 
voltage should be started at less than 34 oi the final value and 
should be brought up gradually to its full value. It should then 
be held for the specified length of time, after which it should be 
reduced slowly to less than l /i of the full value before the circuit 
is opened. 

During this test, windings designed for a voltage of over 
1000 volts must be so arranged that all portions are connected 
together using one of the connections shown on the DS sketch. 
This precaution is necessary as otherwise excessive stresses might 
be induced between parts of the windings, which under normal 
operation would be subjected only to small voltages. 

If the winding has a rated voltage of more than 20,000 volts, 
it is best to use the full series connection during this test. 
Three-phase transformers designed for Y-connection having 

403 



voltage over 20,000 should ordinarily be connected for the 
highest Y-voltage during this test, although exception is made 
in the case of three-phase shell types for operation on Y-Y or 
Y- diametrical systems. 

Failures in Test 

When transformers fail between turns, between coils, 
between windings or from windings to other parts in such a 
manner that it becomes necessary to dismantle them, careful 
examination and tests should be made to determine whether 
failures in other parts have also occurred. 

Transformers failing under high potential should be given 
an induced voltage test before they are dismantled. This test 
should be made in the manner specified for the regular induced 
voltage test. 

Three-phase transformers failing in one phase should be 
given the full high potential test on the other two phases, one 
at a time, both windings of the two phases not under test being 
grounded. If the transformer is of shell type construction, 
induced voltage tests should also be made on each phase sepa- 
rately (whether or not they fail on high potential), with both of 
the other phases short-circuited. 

Three-phase shell type transformers failing between turns 
or between coils so that dismantling is necessary, should have 
the broken phase short-circuited on both high and low voltage 
windings, after which further induced voltage tests should be 
made on the other two phases. Single-phase voltage should be 
impressed on each phase separately while the other phase is 
short-circuited. 

Calculation of Efficiency 

The efficiency of a transformer is the ratio of its net power 
output to its gross power input, the output being at non-induc- 
tive load. The efficiency is to be based on the maximum volt- 
age and kv-a. rating, unless otherwise specified. It may be 
determined by either of two methods: 

1. By the input-output method, or 

2. By the loss method. 

The first method which requires the measurement of the 
input and output on normal load is not accurate on account of 
the small difference between the input and output, and is very 
seldom practicable because of the difficulty of obtaining full 
load. The loss method is, therefore, used exclusively for com- 
mercial work. 

The input includes the output together with the losses which 
are as follows: 

1. The core loss which is determined by the core loss test. 

2. The PR loss of the windings calculated from their 
resistances. 

The core loss may be measured either on the high voltage 
winding or on the low voltage winding. Rated voltage and 
frequency should be used. If the generator does not have a 

404 



sine wave, the loss should be corrected by means of the core 
loss correction outfit. The measurement of loss should be made 
at or near normal room temperature. The PR loss should be 
calculated from the measured resistance reduced to a room 
temperature of 25 deg. cent, unless otherwise specified. The 
rated current of each winding should be squared and multiplied 
by the resistance of that winding, the sum of these losses being 
added together to obtain the total I 2 R loss. See Calculation 
Sheets 29 and 30. 

The rated kv-a. of a transformer is to be considered the 
output and the losses are to be added to this value in order to 
obtain the input. 

For auto-transformers the core loss should be measured in 
the same way as on a transformer, and the PR loss of each sec- 
tion of the winding should be calculated from the rated current 
and resistance at 25 deg. cent. The total loss should be added to 
the rated output to obtain the input. The rated kv-a. of the 
auto-transformer is not the same as the output, but the output 
is always specified by the Engineers. 

Calculation of Regulation 

In constant potential transformers the regulation is the 
ratio of the rise of secondary terminal voltage from full load to 
no load (at constant primary impressed terminal voltage) to 
the secondary full load voltage. Regulation may be determined 
by loading the transformer and observing the rise in secondary 
voltage when the load is thrown off. This method is not satis- 
factory on account of the expense of making the test, and the 
small difference between no load and full load secondary volt- 
ages. Much greater reliance can be placed on results calculated 
from separate measurements of reactance drop and resistance, 
than on actual measurements of regulation. For non-inductive 
load, we have the following formula : 

(per cent IX) 2 
Per cent regulation = per cent IR-\ — — — ^- — - — 

where per cent IR= total resistance drop expressed in per cent 
of rated voltage. 

Per cent IX = total reactance drop expressed in per cent 
of rated voltage. 

For lagging currents, we have the following: 
Per cent regulation = (per cent IR) P + (per cent IX) W+ 
[(per cent IX) P - (per cent IR) W] 2 
200 
where per cent IR= total resistance drop due to load currents 
expressed in per cent of rated voltage, 
per cent IX = total reactance drop due to load currents 
expressed in per cent of rated voltage. 
P = power-factor (cos 6) 
W = wattless factor (sin 0) 
405 



The following table gives the values of W, the wattless 
factor for various values of P, the power-factor: 



p 


w 


1.00 





0.95 


0.312 


0.90 


0.436 


0.85 


0.526 


0.80 


0.60 


0.75 


0.66 


0.70 


0.714 


0.60 


0.80 



The per cent IR is calculated from the rated current and the 
resistance at 25 deg. cent. It may be obtained conveniently by 
dividing the PR loss by ten times the rated kv-a. The per cent 
IX is calculated by taking the square of the per cent impedance 
volts, subtracting the square of the per cent IR and determining 
the square root. See Calculation Sheets 29 and 30. 

In auto-transformers the per cent IR drop should be cal- 
culated in the same way as for a transformer, and may be 
conveniently obtained by dividing the PR loss in watts by ten 
times the equivalent transformer capacity in kv-a. The per- 
cent IX drop should be calculated from the per cent impedance 
in the same way as for a transformer. The auto transformer 
should be connected as a transformer during the impedance 
test. These values of per cent IR and the per cent IX should 
then be multiplied bythe ratio 
rated voltage (h.v. winding) —rated voltage (l.v. voltage winding) 

rated voltage (high voltage winding) 
after which they should be used in the formulae given above 
for transformers. 

INDUCTION REGULATORS 
SINGLE-PHASE INDUCTION REGULATORS 

The IRS, or single-phase Induction Regulator, may be 
cooled by an air blast — it may be placed in a tank and be oil 
cooled — or it may be oil and water cooled. Regulators of this 
type are usually made for the control of single-phase lighting 
circuits. The primary winding is placed in slots on a movable 
core or armature, while the secondary winding is placed in slots 
on a stationary core. The regulator may be wound with any 
even number v of coils. 

The voltage induced in the secondary winding depends upon 
the relative position of the secondary with reference to the 
primary winding, the primary being in shunt and the secondary 
in series with the circuit to be controlled, the voltage of the 
circuit thus being increased or decreased accordingly. Single- 

406 



phase, as well as polyphase regulators have a distributed winding 
for both primary and secondary, but the maximum pole face 
which can be covered by an active winding in a single-phase 
regulator so as to produce the best results, is approximately 
60 per cent. In the neutral position the secondary winding, 
therefore, encloses an area on the primary core not enclosed by 
an active primary winding and the impedance would be extremely 
high if no windings were provided. The slots of the primary 
not used for an active winding are, therefore, filled with a 
short-circuited winding, so that in the neutral position of the 
regulator the current forced through the secondary induces a 
current through the short-circuited winding which reacts upon 
the primary and reduces the impedance. 

Tests Required 

The following tests are made on single-phase regulators: 

Cold resistance. 

Ratio. 

Polarity. 

Core loss. 

Impedance. 

Heat run. 

High potential. 

Induced voltage. 

Xoise tests. 

Tests of auxiliaries. 

These tests are usually made in the order mentioned above. 
The order may be changed, however, if desired. It is considered 
desirable to have the high potential and induced voltage tests 
made last and in the order named. 

Cold Resistance 

Cold resistance should be measured by the methods described 
for transformers, care being observed to obtain accurate measure- 
ments if the rise by resistance is to be calculated at the end of 
the heat run. The resistance measurements should be reduced 
to a room temperature of 25 deg. cent., and entered on the 
test sheet. 

Ratio 

The ratio should be taken with normal voltage on the pri- 
mary, by reading the volts across the secondary with the armature 
in the limiting, maximum boosting, maximum lowering, and 
neutral positions. The feeder volts should be read in each 
position. The number of turns of the handwheel should be 
noted for each position, starting at a limiting position. 

Polarity 

Polarity should be checked against the DS sketch with the 
armature in the maximum boosting position. The regulator 
should boost the line voltage when the handwheel is revolving 
counter-clockwise. 

407 



Core Loss 

On this type of regulator with the permanent short-circuit 
on the armature, the core loss must be taken from the primary- 
winding. The power-factor will be low due to the air gap — - 
hence, considerable care must be taken in making the test. 
The core loss watts and the exciting current should be measured 
at normal voltage and frequency with the armature in both the 
maximum boosting and the neutral position. 

Impedance 

Impedance is always measured on the secondary winding 
as it is impossible to force full load current through the primary 
winding in the neutral position. With the primary short- 
circuited, full load current should be f orced.through the secondary 
and the voltage recorded with the armature in the neutral 
position, maximum boosting position, and position of maximum 
impedance. The positions should be recorded by giving the 
number of turns of the handwheel from a limiting position. 

Heat Run 

The ordinary commercial regulators are given a short- 
circuited heat run without oil. One of the windings is short- 
circuited, and the rotor placed in the maximum boosting or 
maximum lowering position. Currents of sufficient magnitude 
to produce a temperature rise of from 50 to 60 deg. cent, in 20 
minutes, are held in the secondary. The values of currents for 
standard regulators are specified by the Engineers. 

In case a load run is required, the regulator is either con- 
nected as a transformer and placed on a non-inductive load, or 
in case two are available they are given a bucking run with the 
losses supplied from two sources of power. An idle unit is used 
as a basis for calculating temperature rises, if one is available. 

Oil immersed regulators should be filled with oil to the gauge 
line at room temperature. Thermometers should be placed in 
the tank between the second and third ribs — one at the bottom 
and one 2 in. below the gauge line. One thermometer should 
be placed in the top oil, the bulb being immersed about 1 3^ in. 
Room temperature should be recorded at three or four positions 
around the regulator. 

Normal voltage and frequency should be held on the pri- 
mary, and normal current in the secondary. Thermometer read- 
ings should be taken at hourly intervals, and resistance readings 
every two hours, primary and secondary being measured 
alternately. The normal load run should be followed by a 125 
per cent load for 2 hours, unless otherwise specified. 

High Potential 

High potential test is made in the same way as on a trans- 
former. All leads must be connected to one or the other elec- 
trode of the high potential testing set. Standard 1100 to 2500 
volt primary regulators are given a test of 7500 volts for one 
minute between windings, and from windings to frame. 

408" 



Induced Voltage 

The induced voltage test consists of the application of three 
times normal voltage for 10 seconds to the primary winding, 
followed by double normal voltage for 5 minutes. The fre- 
quency should be sufficiently high to keep the exciting current 
within the full load current of the regulator. The armature 
should be placed in the maximum boosting or maximum lower- 
ing position. 

Noise Test 

Every regulator must be carefully tested for noise with 
normal excitation, frequency and load, while the armature is 
moved through its complete range. When the noise exceeds the 
standard which will be set from time to time, the regulator 
should not be passed without the approval of the Engineering 
Department. 

Tests of Auxiliary Apparatus 

The motor and limit switch should be connected in accord- 
ance with the DS sketch, after which they should be operated 
throughout the entire range without load or excitation on the 
regulator. A record should be made of the minimum volts re- 
quired to operate the motor, the amperes at normal voltage and 
the time required to operate it through the entire range. The 
tripping lugs should be adjusted during the test, so as to open 
the limit switch in such a way that the regulator will stop in 
the maximum boosting or maximum lowering position with 
allowance made for standard hunting. There must be suffi- 
cient allowance made to prevent the segment from coming against 
the stop pin when operating. When the tests have been com- 
pleted the bearings should be drained, washed out with kerosene 
oil, and the oil plugs screwed in tight. 

The brake shoes should be oiled, and the brake adjusted for 
hunting of approximately 1 per cent of the total range. The 
hunting should be recorded in turns of the hand wheel. 

The relay switch should be supplied with normal voltage 
at normal frequency, and the amperes measured with the 
armature in the middle position and in the normal operating 
position. A record should also be made of the resistance, and 
the minimum volts required to operate. The minimum volts 
should not exceed 80 per cent of normal. The connections should 
be checked against the DS sketch. The stationary contacts 
should be adjusted so that there is Y%vn. spring at the end of 
the face of the moving element when the armature is against 
the magnet coil. The stationary contacts must bottom in the 
holders which should be placed tight in the support. The 
switch should be given a double voltage test through the magnet 
winding for five minutes at approximately double frequency, 
with the magnet armature closed. 

A high potential test of 1000 volts should be applied for one 
miniate from windings to core, from contacts to frame, and 
between the contacts of the switches. 

409 



Special tests on motors will be called for by the Engineers 
when required. These include starting torque, impedance, 
heat run, minimum volts and amperes and watts with regulator 
loaded. The heat run is made by operating the. regulator at no 
load, reversing at limits during one hour. Normal voltage and 
frequency should be applied to the motor. The brakes should 
be set so as to allow a hunting of about 1 per cent of the total 
range of the regulator, and should be oiled to maintain this 
hunting throughout the run. The room temperature, rise in 
bearings, windings, laminations, rotor, commutator, and brake 
pulley, should be measured by thermometer, and the rise of 
windings by resistance. 

POLYPHASE INDUCTION REGULATORS 

Induction regulators of the IRQ, IRT and IRH types are 
used principally with synchronous converters, but are well 
adapted to control polyphase transmission circuits. As in the 
IRS type, they may be either air blast, oil cooled, or oil and 
water cooled. The primary winding is connected in shunt and 
the secondary in series with the circuit. In the polyphase 
induction regulator, the voltage induced in each phase of the 
secondary is constant, but by varying the relative positions of 
the primary and secondary, the effective voltage of any phase of 
the secondary on its circuit is varied from maximum boost to 
zero, and to maximum lower. 

Referring to Fig. 187 which represents "graphically the volt- 
age of the three phases of a three-phase or IRT regulator, AAA 
equals the line voltage or the e.m.f. impressed on the primary. 
This is shown by the large circle. Let BA, BA and BA equal 
the e.m.f. generated in the secondary coils and constant with the 
impressed e.m.f. This is shown by the three small circles on the 
circumference of the large circle. BBB shows the e.m.f. induced 
in the secondary coils directly in phase with the primary im- 
pressed e.m.f. This is the position of maximum boost. Posi- 
tions CCC represent the neutral position, and DDD the maximum 
lower position. EEE represents a position between neutral and 
maximum lower. 

By changing the position of the armature with respect to 
the field, the secondary voltage may be made to assume any 
phase relation with respect to the primary e.m.f.; it can be in 
series with it or directly opposed to it. This movement of the 
armature is obtained by means of a segment on the shaft which 
meshes with a worm on the small operating shaft. The regulator 
may be arranged for hand operation only, or can be motor- 
operated. Either a direct current or an induction motor may 
be used. The motor is controlled by a small double-pole double- 
throw switch, on the switchboard, to allow the voltage to be 
raised or lowered as desired. 

To stop the regulator on reaching the limits of regulation 
when moving in either direction, a limiting switch is provided, 
which opens automatically. If properly connected, this auto- 
matic cut off, however, does not interfere with movement in the 

410 



opposite direction, which can be obtained by the double-pole 
double-throw switch. 

Tests Required 

The following tests are required on all polyphase regulators: 

Cold resistance. 

Ratio. 

Polarity. 

Core loss. 

Impedance. 

Heat run. 

High potential. 

Induced voltage. 

Xoise test. 




a 

Fig. 187 
REGULATOR DIAGRAM— THREE-PHASE 

The order of tests is immaterial, except that it is best to 
have the induced voltage test follow the high potential test, both 
of them being made after the other tests have been 'completed. 
It is also advisable to check the connection with the DS sketch 
after the tests are made, particularly where permanent con- 
nections are made by the Assembly Dept. after tests. 

Cold Resistance 

The resistance in each phase should be measured and the 
values at 25 deg. cent, calculated and reported on the test sheet. 

Ratio and Polarity 

Two separate tests are required in order to obtain the ratio 
and polarity; (1) ratio of secondary to primary turns, and (2) 
boost and lower and polarity. 

The ratio of turns must be checked by applying normal 
voltage at normal frequency to the primary and measuring the 
induced secondary voltages. 

The primary and secondary should then be connected to 
a source of supply as shown on the DS sketch, normal voltage 
being applied at normal frequency. The feeder voltage of each 

411 



phase should be measured with the armature in the extreme 
maximum boosting, neutral, maximum lowering and other 
intermediate positions. The position of the armature in each 
ease should be recorded in turns of the handwheel from one 
extreme position. The direction of rotation of the handwheel 
for boosting should be recorded. Standard regulators are 
designed for counter-clockwise rotation to boost the voltage. 
If the primary is incorrectly connected to the secondary, 
either an unbalancing of the feeder voltages will be noted, or 
with the feeder voltage balanced, the maximum boost, maximum- 
lowering, etc., will be found at wrong positions of the armature. 
It is possible, although very improbable, that such unbalancing 
may be due to reversed secondary leads. In any event, the 
proper connection must be determined and the leads plainly 
marked so that the necessary changes can be made by the 
Assembly Department. 

Core Loss 

The readings of core loss should be taken on the primary 
side with normal voltage applied at normal frequency. As the 
core loss is not the same in all positions of the armature, the 
maximum and minimum should be found and the readings 
taken at these points. The position of the armature should be 
recorded in turns of the handwheel from one extreme position. 

On IRH regulators having diametrical or double delta pri- 
mary connections, it will be more convenient to make the test 
with three-phase single delta temporary connections. The 
connection used should be noted on the test record. 

Impedance 

The impedance is usually measured by short-circuiting the 
secondary and applying sufficient voltage to the primary wind- 
ing to give full load current. As the impedance is not the same 
in all positions, the maximum and minimum readings should be 
obtained, and the position of the armature noted in each case. 
The impedance of an IRH regulator may be conveniently 
measured by connecting the primary, secondary, or both as 
three-phase. 

Heat Run 

It is customary to give standard regulators a compromise 
run with 150 per cent normal current and 125 per cent normal 
voltage for two hours, the proper cooling medium being used 
throughout. Hot resistances should be measured and the 
temperature rise calculated. Usually the secondary current is 
held at a specified value, but in case it is too large to measure 
it is considered satisfactory to hold the corresponding primary 
current calculated from ratio of turns. 

The ultimate heat runs are usually made with two regulators 
connected according to the motor-generator method, with the 
primaries in parallel and the secondaries in series so connected 
that the primary fields will rotate in the same direction. Normal 

412 



voltage is applied to the primary at the rated frequency. The 
armature of one regulator, called the generator, should be held 
in the maximum boosting position, while that of the other, 
the motor, should be adjusted until the proper secondary current 
is obtained. It is necessary to see that the currents in the pri- 
mary and secondary windings are balanced, particularly when 
the secondary current is large. The primary current will not 
be the same in both regulators. 

If the secondary current is too large to measure, the primary 
current of the one running as a generator should be calculated 
as follows: The theoretical primary current calculated from 
the ratio of turns should be added at an angle of 90 deg. to the 
magnetizing current measured at normal voltage. 

Under such a test, the heating of the regulator running as a 
generator will be equivalent to that under normal load con- 
ditions, whereas the heating of the other will be somewhat 
higher. 

Water cooled regulators should be run with the specified 
amount of water, which should be put in at about average room 
temperature, and the same temperature held throughout the 
run. Air-blast regulators should be furnished with air at the 
specified pressure. The quantity should be measured at the 
start of the run. 

The temperatures should be observed at oil level on the 
outside of the tank, at the bottom of the tank; also the tem- 
perature of the top oil inside the tank. On air-blast regulators, 
the temperature at the top of the tank and at a number of places 
on the windings should be observed. Care should be taken to 
avoid obstructing the passage of air. In case there are likely 
to be hot spots in the windings or connections, thermometers 
should be placed on them. Resistance of one primary and one 
secondary phase should be taken alternately every hour, unless 
the secondary resistance is too large. In that event, the primary 
should be taken every hour. The resistance of each phase should 
be measured at the end of the run, and the rise of temperature 
calculated from the increase in resistance. 

The proper number of single-phase regulators may be used 
instead of a polyphase regulator as the motor on a motor- 
generator run, provided they do not materially change the 
conditions of the polyphase unit under test. The heat run may 
also be made by putting dead load on the regulator, if necessary. 

High Potential 

The high potential test is usually made with the regulator 
hot. On standard 1100 or 2200 volt machines, 7500 volts is 
applied for one minute from primary to secondary and core, and 
from secondary to primary and core. On other regulators, the 
test voltage is specified. The same test voltage is applied 
between secondary phases and between primary phases if they 
can be separated. The test between phases should be made 
from phase 1 to phase 2, from phase 2 to phase 3, and from phase 
1 to phase 3 independently — not from phases 1 and 2 to phase 3, 

413 



etc. The phase not connected during test should be short- 
circuited on itself. 

Induced Voltage 

Triple normal voltage should be applied for 10 seconds to 
the primary winding, followed by double normal voltage for 
5 minutes. The frequency should be sufficiently high to keep 
the magnetizing current within full load current limits. 

The armature should preferably be placed in the maximum 
boosting position. If three-phase connections are used on an 
IRH regulator, care should be taken to see that the proper 
voltage is applied, viz. double volts per turn. 

Noise Test 

The noise test consists of operating the regulator with normal 
voltage and frequency, while the armature is rotated through all 
positions. If a short-circuited heat run is made, the armature 
should be moved over the full range during the run. If it is 
suspected that it may operate in a noisy manner under full load, 
a test should be made under as nearly full load conditions as can 
be obtained. 

Tests of Auxiliary Apparatus 

The operating motor and limiting switch should be connected 
in accordance with the DS sketch and normal voltage applied. 
The current and the time necessary to operate from maximum 
boost to maximum lowering position without load or excitation 
on the regulator should be noted. The minimum voltage 
required to operate the motor under such conditions should also 
be ascertained. 

The brake magnet, which is always designed for the same 
voltage and frequency as the operating motor, should have 
normal frequency voltage applied, and the current measured 
with the armature up. The maximum volts required to operate 
this device should also be determined, and the cold resistance 
should be measured. If the minimum voltage is more than 80 
per cent of normal, the brake should not be passed for shipment. 

All auxiliary parts should be given a high potential test of 
1000 volts for one minute from windings to frame and from 
active switch parts to iron supports. 

BR REGULATORS 

Modern central stations employ alternating current gen- 
erators of large capacity, each generator usually supplying two 
or more districts through independent feeders. One feeder 
may serve a business district, while another from the same 
generator may feed a residential district. As the compounding 
required on any of the feeders depends on the amount of load 
carried by the feeder, and as the load peak occurs at different 
times in different feeders, a device to regulate the feeder voltages 
independently is necessary. 

414 



Type IRS may be used, but the automatic BR feeder 
regulator has been expressly designed for this work. Fig. 188 
shows the circuits. 

The automatic BR feeder regulators can change the line 
voltage quicker and with a smaller power consumption than 
other automatic types. The only moving part is a small and 
light switch arm. The friction of a number of small switch 
contacts constitutes the only turning resistance. 

The moving part of the switch carries a series of fingers, 
the majority of which are always in contact. See Fig. 189. 
Each finger is connected to a corresponding stationary collector 
ring by a brush, and the collector ring is connected to the line 
through a preventive resistance. The resistances connecting 
the fingers to the line prevent excessive exchange currents as 
the fingers pass from contact to contact, and vary the line volt- 
age uniformly. The regulator transformer is oil cooled. 
Tests Required 

The following tests are required: 

Cold resistance. Heat run. 

Ratio High potential. 

Core loss. Induced voltage. 

Impedance. Test of auxiliaries. 

Cold Resistance 

The cold resistance of the primary winding and of each 
half of the secondary winding should be measured exclusive 
of the preventive resistance. The resistance of each of the 
preventive resistances should be measured cold. The spring 
contacts should be insulated from the contact blocks by means 
of a thin sheet of fiber, and the resistance measured between 
the collector rings and the common connection. 
Ratio 

Ratio is taken at no load with full voltage on the primary, 
by reading the voltage across the secondary with the switch 
arm in maximum boosting and maximum lowering positions. 
The voltage should be read between the middle point of the 
secondary winding and each contact block. The polarity should 
also be checked against the standard sketches provided by the 
Engineering Department. 
Core Loss 

The magnetizing current and core loss readings should be 
taken at normal voltage and frequency with the switch contacts 
so arranged that each spring contact will cover one block only, 
or the contacts may be insulated from the blocks by means of a 
thin sheet of fiber. This arrangement is necessary as otherwise 
part of the secondary windings would be short-circuited through 
the preventive resistance and this loss would be included in the 
core loss reading. 
Impedance 

With the primary short-circuited and the switch arm in one 
extreme position, full load current should be forced through the 
secondary and the voltage and watts measured between the 

415 



middle point of the secondary winding and the contact block 
covered by the spring contacts, after which the readings should 
be repeated with the switch arm in the extreme position. The 
same readings should be repeated with the drop, and loss in the 
preventive resistances included. 




Heat Run 

The compromise heat run is made without oil, the primary 
being open-circuited and one-half of the secondary short- 
circuited, while current of sufficient magnitude is forced through 
the other half of the secondary to produce a rise of from 50 to 
60 deg. cent, in 20 to 30 minutes. Resistance should be measured 

416 



at the end of the run and the rise by resistance calculated. The 
two halves of the secondary should be measured separately so 
as not to include the preventive resistance. 

The voltmeter leads should, therefore, be attached to the 
middle point of the two secondary coils and to the extreme 
contact blocks. 



15^^/^ww^Swvww^W^ Tbfeec/er 




i 



0/q/Sw/£c/) 



I I I I II I 



^444- 



■H* 



D/a/ Sw/ich 
flevefoped 



u 



\* 4 4 <4 



Co//ector R/ngs 

Pnevent/ve 
/?es/s6o/7ce 



Fig. 189 
BR REGULATOR 



An ultimate heat run may be made by the motor-generator 
method if two regulators are available at the same time. If 
only one is in test, it may be pumped back on a suitably arranged 
bank of transformers or it may be loaded on a water rheostat. 
In the latter case, apply voltage to the primary, connecting the 
secondary to a water box, adjusting until full load current is 
obtained. The switch must be in one of the extreme positions. 

417 



High Potential 

On 2200 volt regulators, a 7500 volt test for one minute 
should be applied from windings to ground. The test voltage 
will be specified on other regulators. 

Induced Voltage 

Three times normal voltage should be applied for one 
minute, followed by twice. normal voltage for five minutes. 

Tests of Auxiliaries 

The motor should be tested to determine the minimum volts 
required to operate it, and the current consumed when operating 
at normal voltage. 

The clutch coils should have tests to determine the resistance 
of each coil, minimum volts required to operate, and current 
consumed at normal voltage. With the motor and clutch coils 
connected to a line of rated voltage, the switch arm should be 
turned back and forth for one-half hour from one extreme 
position to the other. Operation should be watched closely and 
the time required for turning the switch arm from maximum 
boost to maximum lower should be measured. 

High potential tests should be made before assembly with 
the transformer parts as follows: 

A test of 1000 volts for one minute from clutch coils to frame, 
from active parts of limit switch to frame, from contact blocks 
to switch pot, from collector rings to support, from contact 
fingers to support, and between contact blocks. 

A test of 500 volts for one minute between collector rings 
and also between contact fingers. 

High potential test of 1000 volts should be applied for one 
minute between motor leads and frame, clutch coils and frame, 
and between active parts of limit switch and cover, when the 
final high potential test is made on the assembled regulator. 

REACTANCES 

At the present time reactances are built in several different 
types, the design depending principally upon the use to which 
the reactance is to be put. The largest sizes, called current 
limiting reactances, consist of a winding of bare copper cable 
on a cylindrical concrete core, the turns of this winding being 
insulated from each other by strips of wood, and the whole 
device being cooled by natural air circulation. Reactances of 
large size are also used in connection with the operation of 
synchronous converters, the design in this case being that of a 
polyphase unit wound on a laminated iron core and cooled by 
air blast or by oil circulation. The smaller reactances are used 
mostly in connection with the operation of mercury arc recti- 
fiers. These are wound on iron cores and are cooled by natural 
circulation of the air. 

418 



Tests Required 

The following tests are usually made on reactances: 
Cold resistance. 
Impedance. 
Heat run. 
High potential. 
Double or triple voltage. 

Where there are taps, it is necessary to check the tap ratio 
in the same way as on transformers. 

Cold Resistance 

No special instructions are needed for this other than those 
given for transformers. 

Impedance 

The impedance test consists of forcing normal current 
through the winding and reading the volts and watts. Care 
must be taken to have magnetic material removed at least 
3 ft. from current limiting reactances during this test. 

Heat Run 

The heat run on current limiting reactances is made by 
forcing normal current at normal frequency through the wind- 
ings and continuing the run until temperatures become constant. 
Spirit thermometers only should be used to measure temperature. 

The heat run on reactances for use with mercury arc rectifiers 
usually consist of a 5-hour normal load run with a complete set 
of auxiliary apparatus connected to the mercury arc rectifier 
tube. 

A stability test is usually made at the same time as the heat 
run on reactances for rectifiers. This test consists in the deter- 
mination of the lowest value of direct current necessary to 
maintain the arc in the rectifier tube. 

High Potential 

The high potential test from windings to core is made accord- 
ing to the rules given for transformers. No special instructions 
are needed for reactances. 

Double or Triple Voltage 

This test is made in the same way as on transformers. The 
frequency is increased in order to keep the current within 
reasonable limits. 

SERIES LIGHTING TRANSFORMERS 

Series lighting transformers are used to insulate lamps from 
a high voltage series circuit. They range in capacity from 40 
watts to 2000 watts and the standard ampere ratings are 4, 
5.5, 6.6 and 7.5. As a rule, they are air cooled because the small 
capacity and low losses make it unnecessary to use oil as a 

419 



cooling medium. The primary winding is connected in series 
with a series arc or series incandescent circuit so that under all 
conditions of load on the secondary, the primary carries the full 
current of the circuit. For satisfactory operation of the incan- 
descent lamps connected to the secondary, it is desirable to 
obtain as near constant current in the secondary as possible. 

The tests required are: 

High potential. 

Resistance. 

Core loss and exciting current. 

Open circuit voltage. 

Impedance. 

Regulation. 

Heat run. 

Induced voltage. 

The high potential, resistance and impedance tests are made 
in the manner specified for constant potential transformers. 

Core loss should be measured at normal primary voltage 
and at normal primary current, the secondary being open- 
circuited in each case. The normal voltage is calculated by 
dividing the rated kv-a. by the rated current. 

The open-circuit voltage test is made by reading the voltage 
across the open-circuited secondary with normal current passing 
through the primary. 

Regulation test is made by putting various loads on the 
secondary with rated current passing through the primary and 
measuring the secondary voltage corresponding to each load. 
Readings should be taken at 34, H, Z A an d full voltage. Incan- 
descent lamps should be used for the load. 

The heat run is made with incandescent lamp load. 

The induced voltage test is made by applying three times 
normal voltage to the primary with the secondary open-cir- 
cuited. 



420 



CHAPTER 25 

CALCULATION SHEETS 

The following calculations, which have been made with the 
slide rule, are intended to illustrate the method used in connec- 
tion with testing work. Every effort is made to avoid error 
but this Company does not guarantee their correctness nor does 
it hold itself responsible for any errors or omissions in these 
sheets. 

SATURATION ON A 500 KW., 600 V., 360 R.P.M., 
60 CYCLE, 3-PHASE GENERATOR 



Volts 


Volts 


Amp. 


Speed 


Arm. 


Field 


Field 


R.P.M. 


192 


25 


18.0 ' 


360 


228 


29 


21.0 


360 


253 


32 


23.2 


360 


304 


38 


29.0 


360 


416 


52 


40.0 


360 


495 


62 


48.9 


360 


542 


70 


55.1 


360 


579 


75 


59.8 


360 


597 597 \ 
597 J 
614 


79 


62.0 


360 


83 


65.4 


360 


707 


110 


87.5 


360 


785 


146 


117.0 


360 


755 


130 


102.0 


360 


555 


74 


55.5 


360 


453 


5/ 


43.6 


360 


287 


35 


26.3 


360 


178 


26 


16.1 


360 



CALCULATION SHEET NO. 1 



421 



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CALCULATION SHEET NO. 2 

422 



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CALCULATION SHEET NO. 3 

423 



CALCULATIONS OF DECELERATION CORE LOSS ON A 

3000 KW., 2300 V., 10-POLE, 60 CYCLE, 3-PHASE 

GENERATOR 

Moment of inertia is equal to 705,000 = Wr 2 . 

The normal speed of the turbine being 720, Si is taken equal 
to 730 and S 2 equal to 710. 

Consider curve taken with no field on the machine. (See 
Fig. 59.) 

r 3 or time corresponding to Si =61.6 seconds. 

T4 or time corresponding to 52=82.4 seconds. 

Ta-T z =82.4 -61.6 =20.8. 

(Si -St) 



Kw. loss 



2308 Tr; , 9 W-S 2 *) 



10 10 
2308 



X 



T A -T 3 
705000 X 28800 



2308 (Si+S.) 
10 10 Ta 



4700 



10 10 Ta-T 3 Ta-Tz 

Substituting the value of Ta — Tz in the formula 
4700 



Kw. loss 



= 226 = Friction and Windage 



20.8 

For the curve taken with 77.4 amperes field current 
Ti-Ti =70.6 -52.1 =18.5 

Kw. =-r5-^ = 254 = Core loss + Friction + Windage. 
18.5 

Curves taken with 103, 129 and 142 amperes field are calcu- 
lated similarly, and together with that taken at 77.4 amperes 
field include the constant friction loss and core loss. The two 
losses can be separated. 



Amp. 
Field 
Held 


Tz 
or 
Ti 


r 4 

or 


T, - Tz 

or 
T 2 - Ti 


Si 


5 2 Si 2 -S 2 2 


Fric- 
tion 


Core 
Loss 
and 
Fric- 
tion 


Core 
Loss 


Volts 
from 
Satu- 
ration 





61.6 


82.4 


20.8 


730 


710 28800 


226 


226 








77.4 


52.1 


70.6 


18.5 


730 


710 28800 


226 


254 


28 


1570 


103 


48.2 


66.1 


17.9 1 730 


710 28800 


226 


266 


40 


1990 


129 


44.4 


60.5 


16.1 


730 


710 28800 


226 


292 


66 


2350 


142 


42.8 


58.2 


15.4 


730 


710 28800 


226 


306 


80 


2500 



From the saturation curve the volts armature corresponding 
to the various field currents used can be obtained and a core 
loss curve plotted between volts armature as abscissae and core 
loss as ordinates. 

Si and S 2 are usually assumed at 2 per cent above and 2 
per cent below normal speed. 

CALCULATION SHEET NO. 4 

424 



FIELD COMPOUNDING ON A 150 KW., 250 V. 
225 R.P.M., D-C. GENERATOR 

6 BARS BRUSH SHIFT 



6-POLE, 



Volts 


Amp. 


Volts 


Amp. 


R.P.M. 


Arm. 


Arm. 


Field 


Field 


250 





226 


10.8 


225 


250 


150 


240 


11.65 


225 


250 


300 


270 


12.90 


225 


250 


450 


300 


14.3 


225 


250 


600 


334 


15.9 


225 


250 


750 


370 


17.6 


225 



CALCULATION SHEET NO. 5 

PHASE CHARACTERISTICS ON A 300 KW., 600 V., 750 

R.P.M. , 25 CYCLE 3-PHASE SYNCHRONOUS 

CONVERTER 





NO LOAD 






FULL LOAD 500 AMPS. D-C. 


Volts 


Volts 


Amp. 


Amp. 


Volts 


Volts 


Volts 


Amp. 


Amp. 


Volts 


D-C. 


A-C. 


A-C. 


Field 


Field 


D-C. 


A-C. 


A-C. 


Field 


Field 


600 


378 


315 


0.75 


91 


600 


384 


601 


1.05 


125 


600 


377 


255 


1.25 


150 


600 


383.5 


570 1.25 


150 


600 


376 


210 


1.50 


180 


600 


381 


543 


1.50 


180 


600 


375 


156 


1.75 


210 


600 


380 


520 


2.00 


240 


600 


374 


120 


2.00 


240 


600 


379 


512 


2.25 


270 


600 


373 


85 


2.20 


265 


600 


378 


507 


2.50 


300 


600 


373 


65 


2.30 


275 


600 


378 


505 


2.65 


320 


600 


372 


41 


2.40 


290 


600 


378 


510 2.75 


330 


600 


371 


23 


2.50 


300 


600 


376 


525 3.00 


360 


600 


370 


14 


2.55 


305 


600 


375 


547 3.50 


420 


600 


370 


17 


2.60 


315 


600 


374 


585 4.00 


485 


600 


369 


21 


2.65 


320 


600 


373 


627 4.50 


540 


600 


369 


35 


2.75 


332 


600 


370 


685 5.00 


600 


600 


369 


75 


3.00 


360 












600 


368 


116 


3.25 


395 












600 


367 


170 


3.50 


420 












600 


366 


205 


3.75 


450 













CALCULATION SHEET NO. 6 



425 



SYNCHRONOUS IMPEDANCE ON A 500 KW., 600 V., 
20-POLE, 60 CYCLE, 3-PHASE GENERATOR 



Amp. 


Volts 


Amp. 


Speed 


Arm. 


Field 


Field 


R.P.M. 


224 


15.0 


11.9 


360 


260 


17.8 


13.7 


360 


300 


20.6 


15.8 


360 


352 


23.8 


18.3 


360 


398 


26.9 


20.7 


360 


474 


31.5 


24.5 


360 


480 480 1 
480 J 


32.2 


24.8 


360 


518 


34.8 


26.7 


360 


557 


37.5 


28.2 


360 


704 


47.0 


36.1 


360 


796 


52.8 


40.6 


360 


896 


59.5 


45.7 


360 


1000 


66.5 


51.1 


360 



CALCULATION SHEET NO. 7 



426 





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Motor 



Generator 



Resistance 



CALCULATION SHEET NO. 8 

427 



SPEED, TRACTIVE EFFORT AND EFFICIENCY OF A 
100 H.P. 600 V. RAILWAY MOTOR 



INPUT 


PR 

% 


Core 
Loss 

% 


Gear + 

Friction 

% 


Effici- 
ency 

% 


Miles per 

Hour on 

33 In. 

Wheels 

Gear Ratio 

3.35 




Volts 


Amp. 


Tractive 
Effort 


600 
600 
600 
600 
600 
600 
600 
600 
600 
600 


40 
60 
80 
100 
120 
140 
160 
200 
240 
280 


1.7 
2.5 

3.3 
4.2 
5.0 
5.9 
6.7 
8.4 
10.0 
11.7 


5.3 
4.1 
3.4 
3.0 
2.6 
2.3 
2.1 
1.8 
1.5 
1.3 


30.0 
14.0 
9.0 
7.5 
6.5 
5.7 
5.0 
5.0 
5.0 
5.0 


63.0 

79.4 
84.3 
85.3 
85.9 
86.1 
86.2 
84.8 
83.5 
82.0 


45.0 
35.4 
29.6 
26.2 
23.8 
22.5 
21.3 
19.5 
18.1 
17.2 


170 

407 

687 

984 

1310 

1615 

1960 

2630 

3350 

4040 



Resistances at . . . 75° cent. 

Armature . . 0.107 ohm 

Exciting Field 0.076 " 

Commutating Field 0.050 " 

Brush Contact 0.017 " 

Total 0.250 " 

CALCULATION SHEET NO. 9 



428 



PHASE CHARACTERISTICS OF A 187 KV-A., 2300 V., 

10-POLE, 720 R.P.M., 3-PHASE SYNCHRONOUS 

MOTOR 



Volt Arm. 



Amp. Arm. 



Volts Field 



Amp. Field 



Cycles 





NO LOAD ] 


PHASE CHARACTERISTIC 




2300 


63 


15 


5.5 


60 


2300 


50.76 


24 


10.2 


60 


2300 


33.12 


34.5 


15.6 


60 


2300 


18.6 


44 


19.5 


60 


2300 


8.44 


54 


23 


60 


2300 


1.4-4 


58 


26 


60 


2300 


9.72 


66 


30 


60 


2300 


19.56 


73 


33 


60 


2300 


25.8 


82 


36.5 


60 


2300 


32.52 


85 


39 


60 


2300 


45 


99 


43.5 


60 





FULL LOAD 


PHASE CHARACTERISTIC 




2300 


74.4 


26.5 


11.5 


60 


2300 


69 


31 


13.5 


60 


2300 


57.6 


37 


16.5 


60 


2300 


48.3 


46 


21.5 


60 


2300 


46.5 


60 


28 


60 


2300 


46.5 


62 


28.5 


60 


2300 


49.5 


71 


33 


60 


2300 


52.8 


79 


37 


60 


2300 


58.5 


89 


41.5 


60 


2300 


66.6 


100 


46 


60 


2300 


71.4 


106 


48.5 


60 



125 PER CENT LOAD PHASE CHARACTERISTIC 



2300 


85.8 


30.5 


13.2 


60 


2300 


68.4 


42.5 


19.3 


60 


2300 


60 


53.5 


24.8 


60 


2300 


58.5 


62 


28.7 


60 


2300 


57.9 


63.5 


29.5 


60 


2300 


59.4 


71 


32.8 


60 


3300 


61.8 


79 


36.4 


60 


2300 


65.55 


87 


40.3 


60 


2300 


71.4 


100 


45.6 


60 



CALCULATION SHEET NO. 10 
429 



CALCULATING EFFICIENCY 

Standard efficiency test is made by the method of losses and 
calculations, therefore should be made according to the follow- 
ing : 

D-c. Generator 

Consider a compound wound commutating pole generator 
and 

Let Vl = Volts line. 

Il = Amperes line =78+^9 = /io + /ii. 
I& = Amperes shunt field. 
1 4 = Amperes armature = Il — Ig- 

Is = Amperes series field = lLrs — , 9 P a • 

Jg = Amperes series field shunt = I l — Is- 

TO 

Iio= Amperes commutating field = Ilz 



'(Rn+Rio) 

Jn = Amperes commutating field shunt = Il—Iiq- 
R 5 = Brush contact resistance. 
R& =Hot resistance of shunt field. 



R* = 

Rs = 
R<> = 

Rio — 

Rn = 



armature, 
series field, 
series field shunt. 
" commutating field. 

" " shunt. 

Then the total IR drop=/ 4 Rt+I 4 R 5 +I s Rs+Iio Rio- 
Let Wi = Core loss watts taken from the core loss curve 
corresponding to Vl~\-IR for each load. 
W 2 = Watts brush friction from core loss test. 
If the value taken from test appears inconsistent, calculate 
W2 by the formula: 

W '= 33000 Where . 

F = Circumference of commutator in feet 

N =R.p.m. 

B = Number of brushes 

L =Lb. pressure per brush 

ix = Coefficient of brush friction for the 
particular type of brush used. 
In the case of engine- driven machines or those which are 
furnished without base, shaft or bearings, the bearing friction 
is omitted from the total losses, and is charged against the 
prime mover. 

In nearly every case it is preferable to use the calculated 
brush friction instead of that obtained from test. During a 
short test, the commutator and brush contact surface cannot 
get into as good condition as is obtained after a long period of 
commercial operation. Consequently, the brush friction test 
does not represent the conditions that will exist after the machine 
has been in operation for some time. The coefficient of friction 
determines the value of brush friction, which in turn is deter- 

430 





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CALCULATION SHEET NO. 11 
431 



mined by the condition of the commutator and brush contact 
surface. This coefficient varies considerably at first and only 
reaches a constant value after a considerable - period of opera- 
tion. The coefficient used in the above formula for the calcula- 
tion of brush friction has been obtained by the Company by 
means of exhaustive tests on brushes of different types with 
various pressures and commutators. These tests extended 
over a long period to obtain constant and satisfactory conditions 
for both brush and commutator surface. The resulting values 
of brush friction can, therefore, be relied on to give accurate 
and final results. 

Wz = Bearing friction from core loss test. 

Wb = Watts output =IlX Vl. 
The brush contact resistance, R- , is that taken from a curve, 
made for different types of brushes, corresponding to the brush 
current density per square inch at any given load. 

Brush current density per square inch =t— — -^i : 

Y2 total brush area 

One-half the total brush area = where 

I = Length of brush parallel to the shaft 
iv = Width of brush 
5 = Number of studs 
t = Number of brushes per stud. 
For reasons similar to those just given, the Company has 
made extensive tests to determine the contact resistance of 
different types of brushes, from which curves have been plotted 
with brush current densities as abscissae and either brush con- 
tact resistance per square inch or IR drop in brush contact 
as ordinates. In order to measure the contact resistance directly, 
the commutator would have to be short-circuited and the 
voltage drop measured from the commutator to the surface of 
each brush. This would be a long operation entailing consider- 
able expense. The results also could not be reliable owing 
to the newness of commutator and brushes. It is, therefore, 
preferable to use the brush contact resistance obtained from 
the curves mentioned. 

If Wz= bearing friction from core loss test, then total loss 
in watts = 2 W = W x + W 2 + W 3 + h 2 R 4 + h 2 R 5 + IJR 6 + 
(/e V L - h 2 Re) +h*Rs + h*R 9 + I 1 o 2 Rio+Iu 2 Rn- 

The quantity IsVl-I<?R*=I 2 R loss in the shunt field 
rheostats. 

The watts input W a will then be 

W a =Wb + '2W, where Wb = watts output =IlVl 

Theefficiencv£=-^ 

In case a core loss test is not made, the running light is 
substituted in the formula for the quantity ( Wi + Wi + Wz). 
If the segregation of the losses in the series and commutating 
pole fields and their respective German silver shunts is not 

432 



required the resistances R$ and R$ may be combined to equal 
R S F, likewise Rio and R n to equal R C F- 

The total losses then will be 

2 W = Running light + IJR* + 7 4 2 i? 5 + h Vl + Il 2 RsF 
+Il}RcF. 

To calculate resistances hot when calculating efficiencies, 
the temperature should be obtained from the formula: 

T = (KX rise by thermometer) +25° cent. 
K is the ratio between the rise in temperature by thermometer 
and that determined by resistance measurement. Resistance 
measurements of temperature have been determined by actual 
tests on a large number of different armatures and fields. For 
all armatures, or field spools of revolving field machines K = 1.25. 
For stationary ventilated field spools IT = 1.7. See Calculation 
Sheet 11 and Fig. 70 for form used in calculating and plotting 
efficiency. 

D-c. Motor 

The efficiency of a direct current motor may be calculated 
as follows: 

Using the same nomenclature as above 

U = lL-h 

Watts Input W = IlVl 

W\ = Core loss taken from the core loss curve corresponding 
to Vl-IR 

ThenZW=W l + W 2 + W z +IJR 4 + ISR b +I 6 2 R G + 
(hV L -h 2 R6)+Is 2 Rs+h 2 R*+Iio 2 Rio+Iu 2 Rn 

as before 

Watts output Wb = Tr a — 2 W and 

f- ] 1r 

Wo 
Since motors are always rated according to horse-power 

output 

«-& 

If, as in the case of d-c. generators, only a running light 
is taken and it is desired to combine the resistances of the 
series and commutating pole fields with their respective shunts 
and to combine the losses in the shunt field and rheostats, 
then 

2 W = Running light +h*R i +I?R b +hV L +lL 2 RsF+Il 2 RcF 

In the case of shunt motors 

2 W = Running light +I A 2 R A +Ia 2 R 3 + / 6 Vl 

The remarks made above in reference to the calculation 
of brush friction and brush contact resistance, also in reference 
to the calculation of hot resistances, as well as to all other effi- 
ciency calculations, apply here. (See Calculation Sheet 12.) 

It will be seen from Fig. 75 that motor efficiencies are plotted 
against amperes line as abscissae and per cent efficiency and 
h.p. output as ordinates. The horse-power curve should be 
produced to intersect the abscissae line at running light amperes 
line. 

433 



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PR Armature 
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Total Losses . 
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H.P. Output . 
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Brush Density 
Brush Contact Res 



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CALCULATION SHEET NO. 12 

434 



Synchronous Converter 

The method employed to calculate the efficiency of a standard 
synchronous converter is similar to that used for d-c. generators 
except for the additional PR and friction losses of the a-c. 
brushes. Because of the neutralizing action of the motor and 
generator current it should be noted that only a certain per- 
centage of the PR loss of the armature must be used for cal- 
culating the efficiency of the machine. This percentage varies 
for different machines as follows: 

Single-phase 147% 

Two-phase ....... 39% - 

Three-phase 59% 

Six-phase 27% 



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Fig. 190 
►COEFFICIENT OF FRICTION OF A-C. BRUSHES 



The calculation of the a-c. brush contact resistance requires 
a measurement of the alternating current flowing in the arma- 
ture. This also varies in different types of machines. The 
following are the constants by which the direct current should 
be multiplied to obtain the alternating current. 

For Single-phase 1-41 

Two-phase ....... 0.707 

Three-phase 0.943 

Six-phase 0.472 

As with the d-c. brush contact resistance, a curve must be 
referred to of the a-c. contact resistance. This should be used 
and no direct measurement of resistance attempted. In every 
case the contact resistance should be calculated per ring, the 
total loss being obtained by multiplying by the number of 
rings. 

Brush contact area per ring = width of brush in inches X arc 
of contact in inches X the number of brushes. 

, , , , . Alternating current 

The brush density per ring == r- — ^ Q „ - nrr 

* fe Brush contact area per ring 

* Upper curve taken with copper collector rings. Lower curve taken with 
gun metal collector rings. 

435 



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Volts Line . 
Amps. Line 
Amps. Shunt Field 
Amps. Arm. D-C. 
Amps. Arm. A-C. 
Core Loss . 
Brush Friction D-C. 
Bearing Friction 
PR Armature 


(.59 X D-C. PR) 
PR Brushes D-C. 
PR Shunt Field 
PR Rheostat . 
PR A-C. Brushes 
PR A-C. Brush Fric. 
Total Losses 
Kw. Output 
Kw. Input 
% Efficiency 

Brush Density [ ^_"£ 

Brush Contact f A-C 
Resis. { D-C 



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CALCULATION SHEET NO. 13 
436 



The resistance obtained from the curve, corresponding to 
this value divided by the brush area per ring is the contact 
resistance per ring. 

The a-c. brush friction should be calculated in the same 
manner as used for d-c. measurements, the coefficient of friction 
being taken from a curve. (See Fig. 190.) Calculation Sheet 13 
and Fig. 95 show the form used in calculating and plotting the 
efficiency of a synchronous converter. 

A-c. Generator 

For a-c. generators the method is as follows: 
Let Vl = Volts line 

Wb = Output = V3 VlIl for three-phase and 2 VlIl for 

two-phase. 
Il = Amperes line. 
Ii = Amperes field. 

Rx =Hot resistance of armature between lines. 
R-2 = Hot resistance of field. 
Wi= open-circuit core loss corresponding to Vl+IR on 

the core loss curve 
W 2 = short-circuit core loss corresponding to II on the 

short-circuit loss curve 
Ws = friction and windage obtained from core loss test 
Ii is calculated for each load, as when calculating for 

regulation (See Chapter 9, page 182.) 

\/S 
IR is the drop in the armature = - — Il Ri for three- 
phase machines and Ll Ri for two-phase. 
?W=Wi+i W-2 + Ws+i PL Ri+Ir R-2 for three-phase 
machines 
= Wi+% W 2 + W z +2lL 2 Ri+h' 1 R2 for two-phase ma- 
chines 
Watts input = W a = Wb + 2 W 

Efficiency =777- 

Wz need not be considered if the machine is furnished 
without base, shaft or bearings. 
The above method of calculation is used when the machine 
is to operate at unity power-factor. 

If it is desired to calculate the efficiency at any other power- 
factor the following calculations must be made: 

/L= K L XV5Vr c P-F . and W > = Vj X V LXlLX7o P-F. for 

three-phase machines 
K w 

IL= VlX2XV P-F and W b = 2V L XlLX% P-F. for two- 
phase machines 

7i should be calculated for various power-factors as given 
under regulation. 

437 



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438 



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The change in the line current will affect: 
hi W\, W 2 , and the PR of the armature. See Fig. 87 and 
Calculation Sheet 14. 

Synchronous Motors 

Using the same nomenclature as for a-c. generators the 
following method is used for synchronous motors: 

Ix is either taken from the phase characteristic or is calculated 
W a = watts input = V3 VlIl + I\ 2 Ri for three-phase or 

2 VlIl +I\ 2 Ro for two-phase. 
Wb = watts output = W a ~ 2 W 

Efficiency =ttt 
W a 

W\ = open-circuit core loss corresponding to Vl~ IR on the 
core loss curve. 

Wb 

Horse-power output =^-- 
/4o 

See Calculation Sheet 15 and Fig. 90. 

Induction Motors 

The calculation of the efficiency of induction motors is made 
from the results of the separate special tests taken as given in 
Chapter 12, according to the following method: 

CALCULATING THE CHARACTERISTICS OF AN 
INDUCTION MOTOR 

In calculating the characteristics of an induction motor 
the tabulation given on Calculation Sheet 20 is followed through. 
The slip at maximum load is first calculated and then values 
of slip below that amount are assumed so as to give several 
approximately equally spaced points on the curve and the 
horse power outputs corresponding to these values of slip are 
found by following the tabulated form. Curves are then 
plotted with horse power as abscissae and slip, torque, efficiency, 
etc., as ordinates. 



439 



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Core Loss . 
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PR Arm. . 
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Friction 
Total Losses 
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CALCULATION SHEET NO. 

440 



15 



EXCITATION ON 100 H.P., 440 V., 6-POLE, 500 R.P.M., 
3-PHASE INDUCTION MOTOR 



Volts 


Amperes 


Watts No. 1 


Watts No. 2 

+ 


Total Watts 


544 


57 


13900 


18000 


4100 


497 


46.5 


9550 


13180 


3630 


467 


41.0 


7700 


11000 


3300 


437 


36.5 


6310 


9350 


3040 


398 


31.8 


4800 


7490 


2690 


348 


27 


3300 


5640 


2340 


299 


22.5 


2310 


4300 


1990 


248 


18.4 


1440 


3130 


1690 


197 


14.8 


686 


2110 


1425 


174 


13.2 


497 


1840 


1343 


148 


11.7 


239 


1440 


1201 


124 


10.2 


124 


1240 


1116 


98.5 


9.5 


+ 149 


895 


1044 


81 


9.3 


239 


745 


984 


61.4 


9.5 


273 


696 


969 



SINGLE-PHASE 1-2 



477 


70 




3900 




437 


60 




3430 




397 


52.5 




3060 







SIN 


GLE-PHASE 


2-3 




477 


70 


3950 






437 


60 


3430 






397 


52.5 


3060 





CALCULATION SHEET NO. 16 



441 



POSITION CURVE ON 100 H.P., 440 V., 6-POLE, 500 R.P.M., 
3-PHASE, FORM M INDUCTION MOTOR 



Position 


Volts 


Amp. 


Amp. at Normal 
Volts 


1 


63 


118 


824 


2 


63 


124.5 


870 


3 


63 


134 


935 


4 


63 


121 


845 


5 


63 


116 


810 


6 


63 


130 


907 


7 


63 


129 


900 


8 


63 


119.5 


835 


9 


63 


124 


866 



CALCULATION SHEET NO. 17 



SLIP CURVE ON 100 H.P., 440 V., 6-POLE, 500 R.P.M. 
3-PHASE, FORM M INDUCTION MOTOR 



Volts 


Amp. 


R.P.M. 


Per Cent Slip 


440 


88 


9 


1.8 


440 


118 


14 


2.8 


440 


148 


19 


3.8 


440 


177 


24 


4.8 



CALCULATION SHEET NO. 18 



442 



IMPEDANCE TEST ON 100 H.P.,440 V., 6-POLE, 1200 R.P.M., 
3-PHASE, FORM M INDUCTION MOTOR 



Volts 


Amperes 


Watts. Xo. 1 

+ 


Watts No. 2 


Total Watts 


6.7 


14 


90 





90 


16.6 


36 


425 


25 


400 


21.3 


45 


749 


74 


675 


28.8 


60 


1413 


198 


1215 


34.7 


72.3 


1923 


248 


1675 


38.2 


79.6 


2380 


397 


1983 


44.2 


92.5 


3150 


546 


2604 


49.6 


104 


3920 


596 


3324 


56.5 


118 


5200 


893 


4307 


63.7 


132.5 


6500 


1115 


5385 


74.5 


154 


8740 


1500 


7240 


85.6 


177 


11300 


2010 


9290 


103.7 


214 








115.5 


239 








146 


300 











SINGLE-PHASE 


1-2 




75.7 
66.3 
56 


134.5 

119 

101 


3520 
2765 
2010 





SINGLE-PHASE 2-3 



/ 5.7 


135 


3640 




66.3 


119 


2820 






56 


101 


2010 







CALCULATION SHEET NO. 19 



443 



CHARACTERISTICS OF A 100 H.P., 440 VOLT, 6-POLE, 500 
R.P.M., 3-PHASE, FORM M, INDUCTION MOTOR 

EXPLANATORY NOTES 

b = Susceptance. 

E = Rated terminal volts 

£o = Volts per phase 

e = Counter e.m.f. of rotor in terms of stator 

eso = E — reactive component of e.m.f. 

F = Friction watts from curve 

F = Friction watts per phase 

go = Conductance 

I = Assumed full load amperes per line 

I I = Calculated amperes per phase 

Ih = Core loss component of exciting current 

I m = Exciting current (running light) 

P = Mechanical power of rotor in watts per phase 

P-Fo = Output of rotor in watts per phase 

R — Resistance of stator per phase 

Ri = Resistance of rotor per phase 

Ri = Resistance of rotor per phase in terms of stator 

5 =Slip at normal voltage and current, taken from slip 

curve 

S\ = Assumed slip at various loads 

T — Torque in synchronous watts 

V = Impedance volts at normal amperes, from curve 

W = Impedance watts at normal amperes, from curve 

W\ = Core loss watts 

X = Reactance of stator 

Xi = Reactance of rotor in terms"of 'stator 



FORMULAE 

3-PHASE MOTORS 



b 
E 



eso 
E 



V3 
eso = Eo — ImX 



Fo =— for motor; f — for motor-generator set 



Ih 



eso 
Wx 
3 Eo 
Im = Running light amperes 

I 2 R =7j- (res. between lines at 25 deg.) X(Im 2 ) 

R =3^ (res. between lines at 65 deg.) 
R _ 1.1 EoS 



444 



TT'i = Excitation watts - (7 2 i? + F) 



* = ^(vfc)' : - (i?+ ^ 



_ 21.12 T 

Torque = - 

Syn. r.p.m. 

H.P.= P 



248.7 

Exc. watts 

P-F. (at zero load) = 7= 

A/3 Elm 

Slip at max. output = , 

Ri+V(R+Ri) 2 + (X+X^ 



2-PHASE MOTORS 



£0 

eso — E — ImX 



eso 
£0 =E 



F (F \ 

Fo =— for motor; ( — for motor-generator set 1 



Ih 

go = — 
eso 

Ih = 7r ~^r 
2 Eo 

Im = Running light amperes 

PR =2(res. between lines at 25 deg.) X(im 2 ) 

R =Res. between lines at 65 deg. 

Rl = — -J— 

R - W 7? 
R* ~2P ~ R 

Wi = Excitation watts - (PR + F) 

* -i 

X x =X 



x -iJ(f) f -^+* 



~ 14.08 r 

Torque =- 

Syn. r.p.m. 

373 

■r, -p, , , , n Exc. watts 

P-F. (at zero load) = _ __ 

I Elm 

Ri 

Slip at max. output 



Rx+ViR + RiV + iX+Xiy- 
445 



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CALCULATION SHEET NO. 20 

446 













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H 



CALCULATION SHEET NO. 20 (Continued) 
447 



SUMMARY OF SPECIAL TEST 

EXCITATION RUNNING LIGHT 





Volts 


Amperes 


Watts • 


Polyphase 

Single-phase 

Friction watts 


440 
440 


36.7 
60.5 


3026 

3460 

900 



STATIONARY IMPEDANCE 



Polyphase 
Single-phase 




118 
102 



4375 
2050 



Impedance amp. at rated volts =910. Max. =936. Min. = 
810. Slip (S)=2.8 per cent at normal load of 440 volts, 118 
amperes. 

Resistance between lines at 25 deg. cent. =0.071 ohms; at 
65 deg. cent. =0.082 ohms. 





CALCULATION CONSTANTS 


E n 


= 254. 


X = 0.12926 


Ih = 2.601 


R 


= 0.041 


Xi = 0.12926 


I m = 36.7 


JRi 


= 0.06627 


X x 2 = 0.0167 


e S o =249.26 


£i 2 


= 0.004393 


PR= 143.4 


go = 0.010435 


Rt 


= 0.06377 


Wx =1982.6 
F =300 


b = 0.14725 




SUMMARY OF CHARACTERISTICS 



Per cent load . 


50 


75 


100 


125 


Horse power . 


50 


75 


100 


125 


Amperes line . 


67 


93 


120 


143 


Per cent efficiency 


90.4 


, 91.6 


91.8 


9.1.1 


Per cent power-factor . 


81 


88.8 


92 


92.9 



CALCULATION SHEET NO. 21 



448 



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2 ft. 
2.292 ft. 



CI c 



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CALCULATION SHEET NO. 

449 



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CALCULATION SHEET NO. 

450 



23 



2 ° 

in & 



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CALCULATION SHEET NO. 24 

451 



MOTOR CORE LOSS AND SATURATION ON A 1000 KW., 

600 V., 8-POLE, 375 R.P.M., 6-PHASE 

SYNCHRONOUS CONVERTER 



Direct 


Amp. 
Arm. 










Core Loss 


Volts 


Volts 
Arm. 


Amp. 
Field 


Speed 


IE 


I 2 R 
Arm. 


and 
Friction 


A-C. 
. Side 


258 


54 


2.36 


375 


13920 


30 


13890 


179 


273 


51 


2.50 


375 


13910 


20 


13890 


188 


300 


49 


2.81 


375 


14710 


20 


14690 


210 


348 


44 


3.3 


375 


15300 


20 


15280 


240 


415 


39.5 


4.05 


375 


16400 


10 


16390 


288 


452 


38.5 


4.45 


375 


17400 


10 


17390 


309 


503 


37.6 


5.24 


375 


18900 


10 


18890 


350 


565 


37 


6.22 


375 


20900 


10 


20890 


389 


600 


37 


7.12 


375 


22200 


10 


22190 


421 


630 


37.9 


7.89 


375 


23850 


10 


23840 


439 


660 


38.1 


8.88 


375 


25100 


10 


23090 


462 


687 


41.1 


9.8 


375 


28200 


10 


28190 


479 












BRUSHES 


600 


35.5 


7.1 


375 


21300 


D-c. down, A-c. up 


600 


33.5 


7.1 . 


375 


20100 


D-c. up — (except 2), 
A-c. up 


600 


35.1 


7.1 


375 


21050 


D-c. up — (except 2), 
A-c. down 



D-c. brush friction — 1200. 

A-c. " " — 950. 

Total friction windage from curve 11800. 

Res. of armature at end of C.L. =0.0088. 

CALCULATION SHEET NO. 25 



452 



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CALCULATION SHEET NO. 26 

453 



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CALCULATION SHEET NO. 27 

454 



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CALCULATION SHEET NO. 27 (Continued) 
455 



SHUNT REGULATION ON A 100 KW, 600 R.P.M., 
125 VOLT D-C. GENERATOR 





Volts 


Amp. 


Volts 


Amps. 


Speed 




Line 


Line 


Fid. 


Fid. 


No load, normal volts 


125.0 





66.2 


7.56 


600 


yi load, rheostat as above 


118.8 


200 


62.0 


7.1 


600 


34 load, normal volts . 


125.0 


200 


71.0 


8.1 


600 


}/2 load, rheostat as above . 


114.2 


400 


65.0 


7.5 


600 


}/2 load, normal volts . 


125.0 


400 


73.0 


8.4 


600 


% load, rheostat as above . 


113.1 


600 


66.0 


7.6 


600 


% load, normal volts . 


125.0 


600 


92.0 


10.6 


600 


Full load, rheostat as above 


112.2 


800 


83.0 


9.5 


600 


Full load, normal volts 


125.0 


800 


103.0 


11.9 


600 


No load, rheostat as above 


145.3 





117.0 


13.5 


600 



CALCULATION SHEET NO. 28 



456 



EFFICIENCY AND REGULATION ON HT-60-400- 
6600/11400Y-480 

Connection (primary) 6600, (secondary) 480. 

Temp. deg. cent, (efficiency) 25, (regulation) 25. 

Core loss (per cent) 0.62 at 1.0 P-F. 

Core loss (per cent) 0.775 at 0.8 P-F 

Core loss (watts) 2480. 

PR primary 

PR secondary 

Total loss 4576. 

IR per cent 0.524. 

IZ per cent 4. 

Per cent total loss 1.14, at 1.0 

Kw. input 404.58, at 1.0 P-F. 



2096. 



P-F.; 1.43 at 0.8 P-F. 
324.58 at 0.8 P-F. 



Kw. output 400, at 1.0 P-F.; 320 at 0.8 P-F. 



Per Cent 
Load 



100 PER CENT POWER FACTOR 80 PER CENT POWER-FACTOR 



Test 



Guar. 



Test 



Guar. 







PER 


CENT EFFICIENCY 






150 












125 


98.9 


98.5 


98.6 






100 


98.9 


98.5 


98.6 






- 5 


98.8 


98.4 


98.5 






50 


98.5 


97.9 


98.2 






25 


97.5 


96.2 


96.9 





PER CENT REGULATION 




100 



Resistance at 25 deg. cent, (primary) 3.13, (secondary) 
0.0105. 

CALCULATION SHEET NO. 29 



457 



EFFICIENCY AND REGULATION ON WCT-25-2800- 
38100/66000Y-2300 

Connections (primary) 66,000, (secondary) 2300. 

Temp. deg. cent, (efficiency) 25, (regulation) 25. 

Core loss (per cent) 0.54 at 1.0 P-F. 

Core loss (per cent) 0.676 at 0.8 P-F. 

Core loss (watts) 15140. 

PR primary \ 4Q 0Q 

PR secondary / 

Total loss 56040. 

IR per cent 1.46. 

IZ per cent 4.52. 

Per cent total loss 2, at 1.0 P-F.; 2.5 at 0.8 P-F. 

Kw. input 2856, at 1.0 P-F.; 2296 at 0.8 P-F. 

Kw. output 2800, at 1.0 P-F.; 2240 at 0.8 P-F. 





100 PER CENT POWER-FACTOR 


80 PER CENT POWER-FACTOR 


Per Cent 






Load 












Test 


Guar. 


Test 


Guar. 




PER CENT EFFICIENCY 


150 










125 


97.8 


97.6 


97.3 




100 


98.0 


97.9 


97.6 




75 


98.2 


98.0 


97.8 




50 


98.2 


98.0 


97.8 




25 


97.5 


97.2 


96.9 




PER CENT REGULATION 


100 


1.55 1.7 


3.76 





Resistance at 25 deg. cent, (primary) 36.45, (secondary) 
0.1151. 

CALCULATION SHEET NO. 30 



458 



NOMENCLATURE 
Type 

The following abbreviations are used to designate the type 

of the apparatus listed: 

AB Transformer, air blast, single-phase. 

ABO Transformer, air blast, two-phase. 

ABT Transformer, air blast, three-phase. 

ABH Transformer, air blast, six-phase. 

AS Alternator, revolving armature, single-phase. 

AQ Alternator, revolving armature, two-phase. 

AT Alternator, revolving armature, three-phase. 

AH Alternator, revolving armature, six-phase. 

ASB Alternator, revolving field, single-phase. 

AQB Alternator, revolving field, two-phase. 

ATB Alternator, revolving field, three-phase 

AHB Alternator, revolving field, six-phase. 

ACS Double current generator. 

ASI Synchronous motor, revolving field, single-phase. 

AQI Synchronous motor, revolving field, two-phase. 

ATI Synchronous motor, revolving field, three-phase. 

AHI Synchronous motor, revolving field, six-phase. 

BR Feeder potential regulator. 

C D-c. generator, turbine driven. 

CC D-c. generator, turbine driven, with comm. pole. 

CB Enclosed d-c. motor. 

CBC Enclosed d-c. motor with comm. poles. 

CDM Dynamotor. 

CL D-c. motor or generator. 

CLC D-c. motor or generator with comm. pole. 

CO D-c. motor for crane service. 

CP Air compressor with d-c. motor. 

CPA Air compressor with a-c. motor. 

CPI Air compressor with induction motor. 

CQ Small d-c. motor (Lynn make). 

CV Small d-c. motor (Lynn make). 

CYC Small d-c. motor (Lynn make) with comm. pole. 

CY D-c. motor for mine service. 

DLC D-c. motor or generator with comm. poles. 

DMC D-c. motor or generator with comm. poles. 

GE D-c. railway motor. 

GEA A-c. railway motor. 

GEI Railway induction motor. 

H Transformer (core type) single-phase. 

HQ Transformer (core type) two-phase. 

HT Transformer (core type) three-phase. 

HC Synchronous converter, six-phase. 

HCC Synchronous converter, six-phase, with comm. poles. 

HCB Synchronous converter, six-phase, split pole. 
HCBC Synchronous converter, six-phase, split pole, with comm. 

poles. 

HM D-c. motor for mining service. 

I Induction motor, three-phase. 

459 



IQ Induction motor, two-phase. 

IS Induction motor, single-phase. 

KT Induction motor, three-phase for crane service. 

IRH Potential regulator, induction type, six-phase. 

IRQ Potential regulator, induction type, two-phase. 

IRS Potential regulator, induction type, single-phase. 

IRT Potential regulator, induction type, three-phase. 

ISB Induction alternator, single-phase. 

IQB Induction alternator, two-phase. 

ITB Induction alternator, three-phase. 

LM Mining locomotive. 

MCF D-c. generator or motor with compensating winding in 

the pole face. 

MD D-c. mill motor, totally-enclosed. 

MDO D-c. mill motor. 

MDS D-c. mill motor. 

MI A-c. mill motor induction type. 

MP D-c. generator or motor (multipolar). 

MPC D-c. generator or motor (multipolar) with comm. poles. 

NR Starting compensator for induction motor. 

OC Transformer (oil-cooled) single-phase. 

OCQ Transformer (oil-cooled) two-phase. 

OCT Transformer (oil-cooled) three-phase. 

OCH Transformer (oil-cooled) six-phase. 

PCS A-c. commutator motor for variable speed. 

PCR A-c. commutator motor for regulating. 

QC Synchronous converter, two-phase. 

QCB Synchronous converter, two-phase, split pole. 

QCC Synchronous converter, two-phase, with comm. pole. 

RI Repulsion induction motor. 

TA Voltage regulator for a-c. generators. 

TD Voltage regulator for d-c. generators. 

RLC D-c. motor comm. poles variable speed. 

RC D-c. motor comm. poles for machine tools. 

TC Synchronous converter, three-phase. 

TCB Synchronous converter, three-phase, split pole. 

TCC Synchronous converter, three-phase with comm. pole. 

WC Transformer (water-cooled) single-phase. 

WCQ Transformer (water-cooled), two-phase. 

WCT Transformer (water-cooled), three-phase. 

WCH Transformer (water-cooled), six-phase. 

YC Synchronous converter, split pole, comm. pole. 

Class Rating 

Following the type letters is a set of figures denoting the 
"class rating" of the apparatus. This class rating is variable, 
but for the more common apparatus conforms usually to the 
following: 

Generators, Motors, and Synchronous Converters 

Poles— kw.— speed, e.g., MPC-6-500-720. 

Some ratings give the size of frame, or use an arbitrary number. 

e.g., DLC-201 (30 h.p.-llOO) CB 14; CP-21; GE-210; MD-108. 



460 






Transformers 

Cvcles — kv-a. — volts primary — yolts secondary, e.g., AB- 

25-500-4400-220. 

Potential Regulators 

Poles — ky-a. — cycles — yolts primary — yolts secondary — am- 
peres secondary," e.g., IRH 4-280-25-200-25-3700. 

Form 

Form letters are used to denote details of mechanical con- 
struction or to show that the apparatus was built for some 
particular purpose. 



401 



SUBJECT INDEX 



Subject Page 
ADJUSTMENT: 

Comm. Pole Generators 151 

Non-Comm. Pole Generators 137 

Comm. Pole D-C. Motors 161 

Non-Comm. Pole Motors 157 

Comm. Pole Synchronous Converters 205 

AIR BRAKE APPARATUS 360 

AIR COMPRESSORS 314-317 

Commercial Tests 314 

Complete Tests 315 

Oil Leakage 317 

Special Heat Run 316 

Special Tests 315 

Starting Tests 317 

Wearing in Running 314 

AIR GAP 82 

AIR TABLE FOR BLOWER TESTS, USE OF. . . . 307 

AIR VALVES 360 

ALTERNATORS (See Generators, A-C.) 

AMMETER, A-C 50 

D-C 49 

AMMETER SHUNTS WITH MILLIVOLTMETERS 49 

ANEMOMETERS 26 

ANGLE OF SLINGS, STRESSES DUE TO 58 

APPROVED METHODS OF HANDLING MA- 
CHINES 63-78 

ARMATURE RESISTANCE 112 

Synchronous Converter 190 

ARMATURES, STATIONARY TESTS ON 108 

ASSEMBLY OF MACHINES FOR TEST 58-97 

Approved Methods of Handling 63 

Erecting 79 

Air Gap 82 

Assembly 81 

Balance, Dynamic 91 

Static 90 

Bearings, Filling of 87 

Leakage of 88 

Lubrication of 86 

Oil Gauges for 87 

Temperature Rise of 88, 103 

Thrust 88 

Roller 89 

Belts 92 

Maximum Power to be Transmitted by 92 

Widths, Necessary, of 93 

Blocking 79 

463 



Subject Page 
ASSEMBLY OF MACHINES FOR TEST— Cont'd 

Brushes 83 

Fitting of 84 

Setting of 84 

Spacing of 83 

Bushings 80 

Couplings 80 

End Play, Correcting 96 

Pulleys 91 

Inspection of ■ 92 

Shafts 79 

Truing Commutators 95 

Grinding . 95 

Turning 95 

Hitches 63 

Safe Loads on Eye Bolts 60 

On Manila Ropes and Slings 59 

On Ropes and Chains 60 

On Wire Cable or Slings 59 

Stresses Due to Angle of Slings, Increased 58 

Weights of Various Materials 62 

BAFFLERS, OIL 238, 263 

BAKING COMMUTATORS: 

Comm. Pole D-C. Generators 150 

Non-Comm. Pole D-C. Generators 144 

BALANCE: 

Dynamic 91 

Static 90 

Steam Turbine, Field 246 

Steam Turbine, Wheel 243 

BALANCER SETS 154 

Balancing Tests on 154 

BALANCES 26 

BALLISTIC GALVANOMETERS 31 

BEARINGS: 

Filling of ' 87 

Leakage of . 88 

Lubrication of 86 

Step 238 

Temperature Rise of 88, 103 

Thrust 88 

Roller 89 

Turbine 251 

BELTS 92 

BERM BANK (See Test Tracks) 

BLOCKING 79 

BLOWERS 305-313 

Box Method 311 

Commercial Tests 305 

Complete Tests 305 

Cone Method 310 

464 



Subject Page 

BLOWERS— Cont'd 

Double Pitot Tube (Government) Method 306 

Air Table, Use of , for 307 

Calculation for 308 

Pressure and Horse Power Output Curves by 308 

Endurance Run 305 

Formula? for 311 

General Tests 305 

Maximum Air Delivery Heat Run 305 

Minimum Speed Heat Run 305 

Special Tests 305 

Standard Heat Run 305 

BOOSTERS 5 

For Comm. Pole Svn. Converters. . 206 

BOX METHOD FOR* TESTING BLOWERS 311 

BOXES, WATER (See also Limits) 21 

BREAKDOWN TEST ON INDUCTION MOTORS 134 

BRIDGE: 

Slide Wire 38 

Thomson 40 

Wheatstone 37 

BR REGULATORS (See also Transformers) 414 

BRUSH SETTING: 

Comm. Pole D-C. Generator 152 

Non-Comm. Pole D-C. Generator 136 

Comm. Pole D-C. Motors 161 

Synchronous Converter 191 

Svnchronous Converter with Comm. Poles 205 

BRUSH SHIFTING: 

Comm. Pole D-C. Generator 151 

Non-Comm. Pole D-C. Generator 137 

Series Generator 140 

Non-Comm. Pole D-C. Motor 157 

BRUSHES 83 

by Head of Section, Setting of 98, 136 ' 

BUILDING UP OF D-C. GENERATOR 137 

BUSHINGS 80 

CABLE REELS 353 

CABLE, WIRE: 

Safe Loads 59 

CALCULATION SHEETS 421-458 

Dynamotor, Motor Core Loss 454-455 

Efficiency and Regulation 453 

Generator, A-C, Deceleration Core Loss 424 

Open- Circuit Core Loss 422 

Short- Circuit Core Loss 423 

Efficiency Calculating 437 

Efficiency 438 

Saturation 421 

Synchronous Impedance 426 

465 



Subject Page 
CALCULATION SHEETS— Cont'd 

Generator, D-C, Efficiency Calculating 430 

Efficiency 431 

Field Compounding 425 

Shunt Regulation 456 

Motor, D-C, Efficiency Calculating 433 

Efficiency 434 

Railway, Characteristics 428 

Railway, Input-Output 427 

Motor, Induction, Characteristics, Calculating . . . 439 

Characteristics, Formulae 444 

Characteristics, Results 446, 448 

Efficiency Calculating " 439 

Excitation 441 

Impedance 443 

Position Curve 442 

Slip Curve 442 

Stationary Torque 449 

Motor, Synchronous, Efficiency Calculating 439 

Efficiency - 440 

Phase Characteristics 429 

Running Torque 450 

Starting Test 451 

Synchronous Converter, Core Loss and Saturation . 452 

Efficiency Calculating 435 

Efficiency 436 

Phase Characteristics 425 

Transformer, 3-Phase Core Type, Efficiency and 

Regulation 457 

3-Phase Water Cooled, Efficiency and Regula- 
tion 458 

CALIBRATION CONSTANT FOR INSTRU- 
MENTS 46 

CARBONS FOR PROJECTORS 380 

CHAINS, SAFE LOAD ON 60 

CHARACTERISTIC CURVES ON INDUCTION 

MOTORS 222 

CIRCUIT BREAKERS, RAILWAY 371 

CLASSES OF RESISTANCE MEASUREMENTS 36 
COMMUTATION: (See also Adjustment) 

Chart for 138 

On Non-Comm. Pole D-C. Generators 137 

COMMUTATOR: 

Eccentricity of 136 

Grinder 95 

Truing 95 

COMPASS 4 

COMPLETE TEST ON VARIOUS TYPES OF 

MACHINES (See Type Heading) 
COMPENSATORS: 

For Three- Wire Generators 149 

Starting 347 

466 



Subject Page 
COMPOUNDING: 

Comm. Pole D-C. Generators 153 

With Reactance (Syn. Converters) . . 200 

D-C. Generator (Cold) 138 

D-C. Generator Field 145 

COMPOUNDING CURVE (D-C. GENERATOR).. 145 

COMPRESSORS (See Air Compressors) 

CONDENSER HEAT RUN (Zero Power-Factor). 180 

CONE METHOD FOR TESTING BLOWERS 310 

CONNECTION BLOCKS (A-C. Generators) 173 

CONNECTION BOXES (RAILWAY) 364 

CONSTANT POTENTIAL TRANSFORMERS. ... 384 

CONTACTOR BOXES 370 

CONTACTORS: 

A-C 346 

D-C 345 

Railway 364 

CONTROL": 

For Projectors, Types of 374 

Industrial (See Industrial Control) 
Train (See Train Control) 
CONTROLLERS: 

Printing Press 346 

Railway 361 

Trucklight 380 

CONVERTERS, SYNCHRONOUS 190-207 

Brush Setting 191 

Commutating Pole 205 

Adjusting Shunt 205 

Boosters for 206 

Setting Brushes 205 

Complete Test 200 

Compounding Test with Reactance 200 

Core Loss 200 

End Plav Device 191 

Heating Tests 192 

D-C. Booster Method (Circulating Current) . 195 

Potential Regulator Method (Feeding Back) . 196 

A-C. Loss Supply 197 

D-C. Loss Supply 196 

Water Box Method 192 

Current Ratio A-C. to D-C 193 

Phase Characteristics 193 

Precautions in Wiring 193 

Starting up from A-C. End 193 

Input-Output Efficiency 202 

Inverted Converters 203 

Motor-Converters 207 

Phase Rotation 191 

Preliminary Tests 190 

Armature Resistance 190 

467 



Subject Page 
CONVERTERS, SYNCHRONOUS— Cont'd 

Equalizer Spacing 190 

Pulsation Test 201 

Short Commercial Test • 190 

Special Tests 198 

Saturation 198 

Starting Test, A-C 198 

Starting Test, D-C 198 

Synchronous Impedance 198 

Speed Limiting Device 191 

Split Pole 203 

Core Loss and Saturation 204 

Heating Tests 205 

Phase Characteristics, No Load 203 

Phase Characteristics, Full Load 204 

Running Light 205 

Voltage Range Curves 204 

Standard Efficiency 200 

Voltage Ratio 191 

Using Reactance 192 

COOLING-OFF TESTS ON RAILWAY MOTORS 169 
CORE LOSS: 

Belted . 123 

Deceleration 128 

Running Light 122 

On Various Types of Machines (See Machine 
Type Heading) 

COUPLERS 370 

COUPLINGS 80 

CRANE MOTOR RUNS 209 

CURRENT: 

From Frame to Shaft ' 173 

£ Measurement of 49 

In Three-phase Circuits 50 

Ratio of Syn. Converters 193 

Transformers 50 

CUT-OUTS 364 

D-C. GENERATORS (See Generators, D-C.) 

D-C. MOTORS (See Motors, D-C.) 

DECELERATION CORE LOSS 128 

DEFECTS: 

Reporting and Correcting 103 

Steam Turbine 273 

DEVELOPMENT TESTS (RAILWAY MOTORS) 165 

DIVING LAMPS 380 

DOUBLE PITOT TUBE METHOD (BLOWER 

TESTS) 306 

DOUBLE SPEED (See Over-Speed) 

DROP ON SPOOLS Ill 

DYNAMOTORS 170 

468 



Subject Page 

EFFICIENCY: 

On Various Types of Machines, Standard (See 
Machine Type Heading) 

Transformer 384 

Calculation of 404 

ELECTRICAL POWER, SHOP 5 

ELECTRIC LOCOMOTIVES 300 

ELECTROMOTIVE FORCE, MEASUREMENT OF 45 

EMERGENCY GOVERNORS 247 

END PLAY: 

Correcting 96 

Device, Magnetic 117 

Device, Mechanical 118 

ENGINE: 

Indicator, Steam 26 

Marine (See Marine Engine) 

Regulation in Compounding Generators, Allow- 
ance for 140 

EQUALIZERS 136 

For Svn. Converters, Spacing of 190 

EQUIPMENT 5-23 

Boosters 5 

Electrical Power 5 

Exciters 6 

Used as Boosters 6 

Field Rheostats 23 

Floor Stands : 14 

High Potential Testing Sets 7 

Measuring Sets 6 

Motor-Generator Sets 7 

Safety Devices 13 

Shop Motors and Generators 12 

Steam Power 10 

Switchboards 14 

Testing Tables 19 

Transformers 23 

Water Boxes 21 

EQUIVALENT LOAD: 

A-C. Generators 179 

D-C. Generators 144 

Induction Motors 210 

ERECTING 79 

EXCITATION: 

Curves (Induction Motors) 211 

Readings (Induction Motors) 209 

EXCITERS 153 

Used as Boosters 6 

EXCITING CURRENT OF TRANSFORMERS. . . 393 

EYEBOLTS, SAFE LOAD ON 60 

FAILURES OF TRANSFORMERS IN TEST 404 

FAN TESTS (See Blowers) 

469 



Subject Page 
FEEDING BACK: 

A-C. Generators 177 

D-C. Generators ■...." 141 

D-C. Motors 158 

Induction Motors 209 

Synchronous Motors 196 

FIELD: 

Balance (Steam Turbine) 246 

Compounding (D-C. Generators) 146 

Resistance, Measurement of 112 

Rheostats 23 

Tests on 343 

FINGER PRESSURE (Railway Contactors) 366 

FLOOR STANDS 14 

FLOW TANKS 279 

FOCAL LENGTH OF PROJECTOR MIRRORS. . 377 

FORMULA FOR BLOWER TEST 311 

FREQUENCY: 

And Speed 32 

Indicators 33 

FRICTION: 

By Free Running (Electric Locomotive) 304 

From Coasting (Electric Locomotive) 304 

Train 304 

FUSE BOXES 369 

FUSES, RAILWAY 369 

GALVANOMETER, BALLISTIC. . . 31 

GAUGES: 

Pressure 27, 276 

Vacuum. . : 27 

Oil 87 

GENERAL TESTS (INDUCTION MOTORS) 223 

GENERATORS, A-C 172-182 

Commercial Tests 172 

Connection Blocks 173 

Magnetic Leakage (Current from Frame to 

Shaft) 173 

Phase Rotation 172 

Synchronous Impedance 172 

Heating Tests 175 

Actual Load 176 

Feeding Back 177 

Power-Factor Run 176 

Equivalent Load 179 

Long Commercial Test 181 

Open Delta Run 179 

Open-Circuited Run 179 

Short-Circuited Run 179 

Zero Power-Factor Run 180 

Location of Keyway 181 

Marine Engine- Driven (See Marine Engines) 

470 



Subject Page 
GENERATORS, A-C— Cont'd 

Preliminary Tests 172 

Special Tests. 181 

Standard Efficiency 181 

Static Test 182 

Turbine Driven (See Turbines) 

Voltage Regulation 181 

Wave Form 182 

GENERATORS, D-C 136-156 

Balancer Sets 154 

Building up of 137 

Refusal to Generate 137 

Series Generator 137 

Commutating Pole 149 

Baking Commutators on 150 

Compounding, etc 153 

General Notes on 149 

Spacing of Poles of 149 

Locating Neutral on 150 

Shunt Adjustment of 151 

Brush Position, Marking of 152 

Grid Shunts, Position of 152 

Inductive Shunt 152 

Motor Operation 153 

Shifting Brushes 151 

Trammel 152 

Three- Wire 153 

Commutator, Eccentricity of 136 

Equalizers for 136 

Exciters 153 

Stability Test 153 

General Instructions on 136 

Marine Engine- Driven (See Marine Engines) 

Non-Commutating Pole 137 

Complete Test 147 

Heating Tests on 140 

Actual Load 140 

Circulating Current 143 

Feeding Back 141 

Electrical Loss Method 142 

Into Shop Circuit 142 

Mechanical Loss Method 141 

Sets 142 

Water Box Method 140 

Equivalent Load 144 

Baking Commutators 144 

Normal Load Heat Run 144 

Overload Heat Run 145 

Miscellaneous Tests on 145 

Compounding Curve 145 

Field Compounding 146 

High Potential 145 

471 



Subject Page 
GENERATORS, D-C— Cont'd 
Non-Commutating Pole 

Miscellaneous Tests on 

Rheostat Data 145 

Running Light 146 

Shunt Regulation 145 

Stud Potential Curve 147 

Shunt Adjustment of 137 

Commutation 137 

Chart 138 

Setting Brushes for 136 

Shifting Brushes for 137 

Compounding, Cold 138 

Engine Regulation, Allowance for . . 140 

Reversed Series Field 138 

Series Generator, Series Characteristic . . 140 

Shifting Brushes 140 

Special Tests 147 

Standard Efficiency 147 

Three- Wire 147 

Revolving Compensator 149 

Unbalanced Readings 149 

Preliminary Tests on 136 

GENERATORS, SHOP MOTORS AND 12 

GOVERNOR: 

For Air Brake Apparatus 361 

For Steam Turbine, Emergency 247 

For Steam Turbine, Operating 251 

For Marine Engines 295 

Tests (Steam Turbines) 247 

GRID SHUNTS, POSITION OF 152 

GRINDER, COMMUTATOR 95 

HEATING TESTS: 

On Various Types of Machines (See Machine 
Type Heading) 
HEAT RUNS: (See also Heating Tests) 

Preparation for 101 

On Electric Locomotives, Service 303 

HIGH POTENTIAL 113 

On Various Types of Apparatus (See Apparatus 
Type Heading) 

Testing Sets 7 

HIGH RESISTANCE MEASUREMENTS 42 

HIGH SPEED TEST (See Over Speed) 

HITCHES 63 

HUNTING OF COMM. POLE D-C. MOTORS.... 162 

HYDROMETER 27 

IMPEDANCE: 

Constant Potential Transformers 393 

Curves (Induction Motors) 214 

472 



Subject Page 

I M P E D A X C E— Cont ' d 

Position Curve (Syn. Motors) 188 

Readings on Induction Motors, Stationary 209 

INDICATOR: 

Diagrams, Marine Engine 296 

Frequency and Speed 33 

Phase Rotation 25 

Slip 27 

Steam Engine 26 

IXDUCED VOLTAGE: 

Constant Potential Transformers 403 

Synchronous Motors 183 

Synchronous Condensers 193, 198 

INDUCTION GEXERATOR RUNS 209 

Induction: 

Motors (See Motors, Induction) 
Regulators (See Transformers) 

IXDUCTIVE SHUNTS 152 

IXDUSTRIAL CONTROL APPARATUS 343-352 

Compensators, Starting 34/ 

Heat Runs 351 

Insulation Tests 352 

Magnetizing Current 351 

Ratio 347 

Contactors, A-C 346 

D-C 345 

Controllers, Printing Press 346 

High Potential Tests 347 

Panels, A-C 345 

D-C 345 

Rheostats, Field 343 

For Split Pole Syn. Converters 344 

Starting and Regulating, Hand Operated .... 344 

Shipment 347 

Starters, Automatic 344 

IXDUSTRIAL LOCOMOTIVES 354 

INPUT-OUTPUT TESTS 130 

On Various Types of Machines (See Machine 
Type Heading I 
INSPECTION: 

Of Pulleys 92 

Of Apparatus, Preliminary 98 

Of Wiring ' ' 99 

INSTRUMENTS FOR STEAM TURBIXE TESTS 233 

INSTRUMENTS, USE AXD CARE OF 24-57 

Anemometers 26 

Balances 26 

Ballistic Galvanometer 31 

Care of 24 

Compass 4 

473 



Subject Page 
INSTRUMENTS, USE AND CARE OF— Cont'd 

Current, Measurement of 49 

In 3-Phase Circuits - 50 

A-C. Ammeters 50 

Transformers 50 

D-C. Ammeters 49 

Ammeter Shunts with Millivoltmeters 49 

Electromotive Force, Measurement of 45 

Potential Transformers 48 

Potentiometer 45 

Stray Fields, Test for 47 

Voltmeters 45 

Calibration Constant 46 

Millivoltmeters 46 

Hydrometer 27 

Indicators, Steam Engine 26 

Manometers 26 

Phase Rotation Indicator 25 

Planimeter 26 

Power, Measurement of • 51 

Wattmeters 51 

Phase Angle, Correction for 55 

Power-Factor, Measurement of 56 

Pressure Gauges 27 

Resistance Measurements 36 

Classes of 36 

High Resistance Measurements 42 

High Resistance D-C. Voltmeter. . . 42 

Insulation Resistance Testing Sets . . 42 

Megger 44 

Low Resistance Measurements 40 

Drop Method (D-C.) 40 

Thomson Bridge 40 

Medium Resistance Measurements 36 

Slide Wire Bridge , 38 

Ohmmeter 38 

Wheatstone Bridge 37 

Primary Standard of 36 

Unit Employed 36 

Working Standard 36 

Scales 26 

Slip Indicator 27 

Speed and Frequency 32 

Speed and Frequency Indicators 33 

Primary Standard 32 

Speed Indicators 33 

Tachometers 32 

Torque Recorder, Stationary < . . 29 

U-Tubes 26 

Vacuum Gauge 27 

Wave Shapes 34 

Oscillograph 35 

474 



Subject Page 

INSULATION RESISTANCE 112 

Testing Sets 42 

On Various Types of Apparatus (See Apparatus 
Tvpe Heading) 

INSULATORS, PORCELAIN 358-359 

Applying High Potential, Methods of 358 

Inspection 358 

Switchboard Dept., Routine Tests for 358 

Tubes 359 

INTERMITTENT RUNS ON INDUCTION 

MOTORS 209 

INTRODUCTION 4 

INVERTED CONVERTERS 203 

JUMPERS (Railway) 371 

KEYWAY, LOCATION OF 181 

KEYBOARDS 380 

LEAKS IN STEAM TURBINES, WATER 233 

LIMITS: 

Air Gap 83 

Bearings: 

Maximum Temperature Rise Allowed 88 

Maximum Temperature Rise Allowed on 

Commercial Run 103 

Belts: 

Maximum Power to be Transmitted 92 

Maximum Speed Allowed 94 

Compensators: 

Magnetizing Current 351 

Ratio 351 

Core Loss: 

Open-Circuit, Low Limit of Highest Reading 125 

Short-Circuit, Low Limit of Highest Reading 128 

Drop on Spools: 

A-C. Machines Ill 

D-C. Machines Ill 

Exciters: 

Low Limit of Voltage with Full Field 153 

Stability, Voltage Variation in 153 

Governors, Operating: 

Limits of Operation 263 

Manometers: 

Range of Usefulness 26 

Pole Spacing, Commutating: 

Variation 82 

Resistance: 

Grid for Mining Locomotive, Variation in . . . 353 

Cold, Railway Motors 163 

Coil, Reversers '. 363 

Coil, Reversers, Supply Spools 363 

475 



Subject Page 

LIMITS— Cont'd 
Rheostats: 

Solenoid Operated, Voltage for Operation .... 343 

Starting and Regulating, Hand Operated, 

Voltage for Operation 344 

Saturation: 

Range of Curve 120 

Shaft Pressure: 

Usually Required 80 

Lowest Allowable 80 

Speed: 

Marine Sets, Regulation 293 

Motors, S.W. or C.W. Comm. Pole, Variation 

from Rated, Cold 161 

Motors, S.W. or C.W. Comm. Pole, Variation 

from Rated, Hot 161 

Motors, S.W. or C.W. Comm. Pole, Variation 

from No Load to Full Load 161 

Motors, S.W. Non-Comm. Pole, Variation 

from Rated, Cold 158 

Motors, S.W. Non-Comm. Pole, Variation 

from Rated, Hot 158 

Motors, C.W. Non-Comm. Pole, Variation 

from Rated, Hot 158 

Motors, S.W. Non-Comm. Pole, Speed Regu- 
lation 158 

Motors, Series and Railway, Variation from 

Rated, Hot 163 

Shop Machines, Maximum Allowable 13 

Voltage Balance: 

' Of Balancer Set 154 

Water Box: 

Load 140 

Voltage 176 

LOAD LOSS 132 

LOADING VARIOUS TYPES OF* MACHINES (See 
"Heating Tests" Under Type Heading) 

LOADS, SAFE 59, 60 

LOCATING NEUTRAL: 

Comm. Pole D-C. Generators 150 

Comm. Pole D-C. Motors 161 

LOCATION OF KEYWAY 181 

LOCOMOTIVES, ELECTRIC 300 

LOCOMOTIVES, MINING AND INDUSTRIAL. . 353-357 

Industrial 354 

Mining 353 

Cable Reels 353 

Winding Devices 354 

Storage Battery 355 

LONG COMMERCIAL TEST 

A-C. Generator 181 

Induction Motors 223 

476 



Scbject Page 

LOW RESISTANCE MEASUREMENTS 40 

LUBRICATION: 

Bearings 86 

Marine Engines 288 

Turbines 233 

MAGNETIC LEAKAGE 173 

MAGNETIZING CURRENT OF STARTING COM- 
PENSATORS 351 

MANOMETERS 26 

MARINE ENGINE SETS 285-299 

Engine 288 

General Instructions 298 

Governor 295 

Indicator Diagrams 296 

Lubrication 288 

Operation 294 

Packing 298 

Pressure, Steam 288 

Starting up 293 

Tests 293 

Valves 293 

Generator 299 

MAXIMUM OUTPUT 133 

MEASURE. COLD, STEAM TURBINE GENER- 
ATORS : 269 

MEASURING SETS 6 

MEASUREMENT OF VARIOUS QUANTITIES 
(See the Quantitv i 

MEDIUM RESISTANCE MEASUREMENTS 36 

MEGGER 42 

METERS i See Instruments) 

MILLIVOLTMETERS 46 

MINIMUM PICK UP, RAILWAY CONTACTORS 366 

MINING LOCOMOTIVES 353 

MIRRORS FOR PROJECTORS 377 

MOTOR AND GENERATOR OPERATION (D-C. 

Motors) 162 

MOTOR-CONVERTER 207 

MOTOR FIELDS, WIRING 99 

MOTOR-GENERATOR SETS, SHOP 12 

MOTORING STEAM TURBINES 212 

MOTOR OPERATION (D-C. Generator) 153 

MOTORS | D-C.) 157-171 

Commutating Pole 161 

Adjustment for Commutation 161 

Hunting 162 

Motor and Generator Operation 162 

Running Light 162 

Setting Brushes 161 

Speed Variation 161 

Dynamotors 170 

477 



Subject Page 
MOTORS (D-C.)— Cont'd 

Non-Commutating Pole 157 

Adjustment for Speed and Commutation .... 157 

Heating Tests 158 

Loading for. 158 

Running Light 159 

Special Tests 159 

Speed Curve, Hot 159 

Shifting Brushes 157 

Speed Regulation 158 

Standard Efficiency 161 

Preliminary Tests 157 

Series and Railway Motors 163 

Commercial Tests 167 

Complete Tests 164 

Cooling-off Tests 169 

Development Tests 165 

General Tests 163 

Input-Output 168 

Special Tests 165 

Core Loss 165 

Loading, Method of 167 

Saturation 165 

Speed Curves 165 

Thermal Characteristics 165 

Standard Efficiency Test (Series Motors) .... 168 

Tractive Effort 169 

Starting up 157 

Variable Speed 162 

Ventilation Tests 171 

MOTORS, INDUCTION 208-226 

Commercial Tests 208 

Complete Test 223 

General Test 223 

Heating Tests 209 

Actual Load Runs 209 

Crane Motor 209 

Induction-Generator 209 

Intermittent 209 

Equivalent Load Runs 210 

High Potential 226 

Input-Output and Power-Factor Test. . 223 

Electrical Load Method 225 

String Brake Method 223 

Long Commercial 223 

Preliminary Tests 208 

Special Overload Heat Run 223 

Special Tests 211 

Characteristic Curves 222 

Excitation Curve 211 

Impedance Curve 214 

Position Curve 215 

478 



Subject Page 
MOTORS, INDUCTION— Cont'd 
Special Tests 

Slip Curve 217 

Starting Test 222 

Torque, Stationary 220 

Standard Efficiency and Power-Factor Test 223 

MOTORS, SYNCHRONOUS 183-189 

Commercial Tests 183 

Complete Tests 188 

Heating Tests 183 

Actual Load 185 

Equivalent Load 185 

Impedance-Position Curve 188 

Phase Characteristics 183 

Preliminarv Tests 183 

Special Tests 185 

Core Loss 185 

Saturation 185 

Starting 185 

Svnchronous Impedance 185 

Wave-Form 185 

Standard Efficiency 188 

Starting Up 183 

Torque Tests 188 

Running 188 

Stationary 188 

MOUNTING MOTORS ON TRUCKS 302 

MS SWITCHES 363 

MU TRIPPING SWITCHES 364 

NEUTRAL, LOCATING: 

Comm. Pole D-C. Generators 150 

Comm. Pole D-C. Motors 161 

NOMENCLATURE: 

General 459 

Turbine 227 

NORMAL LOAD HEAT RUN (D-C. GENERATOR) 144 

NUMBERING FIELD SPOOLS 112 

OHMMETER 38 

OIL: 

Flow (Steam Turbines) 235 

Gauges 87 

OILING (See Lubrication) 

OPEN CIRCUIT RUN (A-C. GENERATORS) 179 

OPEN-DELTA RUN (A-C. GENERATORS) 179 

OPERATING GOVERNORS, STEAM TURBINE 251 
OPERATION, OBSERVATION AND COMMENTS 

ON 103 

OSCILLOGRAPH 35 

OUTPUT TEST, MAXIMUM 133 

OVERLOAD HEAT RUN (D-C. GENERATOR)... 145 

OVER SPEED TEST 135 

479 



Subject Pa 

PACKING: 

Marine Engine - 2! 

Rings, Carbon 2< 

PANELS: 

A-C 3- 

D-C 3^ 

PHASE ANGLE IN WATTMETERS, CORREC- 
TION FOR I 

PHASE CHARACTERISTICS ON VARIOUS MA- 
CHINES (See Machine Type Heading) 

PHASE ROTATION: 

Indicator 25 

On A-C. Generators 172 

On Syn. Converters 191 

On Transformers 390 

PIPING, STEAM, EXHAUST AND OIL 232 

PITOT TUBE METHOD FOR BLOWER TESTS, 

DOUBLE 306 

PLANIMETER 26 

POLARITY: 

Of Generators and Motors Ill 

Of Transformers 386 

POLE SPACING, COMMUTATING 149 

PORCELAIN INSULATORS 358 

POSITION CURVE, INDUCTION MOTORS 215 

POTENTIAL CURVE: 

Between Brushes . 134 

Stud 147 

POTENTIOMETER 45 

POWER: 

Electrical 5 

Measurement of 51 

Steam 10 

POWER-FACTOR: 

Measurement of 56 

POWER-FACTOR RUN: 

On A-C. Generator 176 

On Syn. Motor 180, 185 

PRELIMINARY TEST ON VARIOUS MACHINES 
(See Machine Type Heading) 

PREPARATION OF APPARATUS FOR TEST. . . . 98-105 

Defects, Reporting and Correcting 103 

Heat Runs, Preparation for 101 

Calculating Temperature Rise on 103 

Placing Thermometers for 101 

Inspection, Preliminary 98 

Operation, Observations and Comments During. . 103 

Starting Up 100 

Stationary Apparatus 105 

Temperature Coils 103 

Wiring 98 

480 



Subject Page 
PREPARATION OF APPARATUS FOR TEST— Cont'd 
Wiring 

Inspection bv Head of Section 99 

Motor Fields _ 99 

Transformers, Grounding of 100 

PREPARATION FOR TEST: 

Steam Turbines 233 

Transformers 385 

PRESSURE: 

Gauges 27 

Steam (Marine Engines) 288 

PRINTING PRESS CONTROLLERS 346 

PROJECTORS 373-381 

Adjustment 375 

Carbons 380 

Inspection 373 

Mirrors, Focal Length of 377 

Rheostats 377 

Signal Apparatus. 380 

Diving Lamps 380 

Keyboards 380 

Trucklight Controllers 380 

Tvpes of Control 374 

PULL" CURVE: 

Electric Locomotive 302 

Railwav Contactors 367 

PULLEYS 91 

PULSATION TEST (SYN. CONVERTERS) 201 

PUMP BACK (See Feeding Back) 

QUANTITY OF OIL FOR BEARINGS 89 

RAILWAY MOTORS (See Motors, D-C.) 

RATIO: 

On Starting Compensators 347 

On Syn. Converters, Current 193 

On Syn. Converters, Voltage 191 

On Induction Motors, Voltage 209 

On Transformers 391 

REACTANCE: 

Changing Ratio of Syn. Converters with . . .• 192 

Compounding Svn. Converters with 200 

REACTANCES (See Transformers) 

RECORDS, TESTING 106 

REELS, CABLE 353 

REGULATION: 

Engine, Allowance for 140 

Shunt (D-C. Generator) 145 

Speed (Comm. Pole D-C. Motors) 161 

Speed (Non-Comm. Pole D-C. Motors) 158 

Voltage (Transformers) 384 

Voltage (Transformers), Calculation of 405 

Voltage (A-C. Generators) 181 

481 



Subject p AGE 

REGULATORS, INDUCTION (See Transformers) . . 406 

REGULATORS, VOLTAGE 318-342 

Adjustment 321 

Heat Runs 322 

High Potential 322 

Principle of Operation, General 318 

TypeTA 318 

Form A 2 318 

Principle of Operation 318 

Form F 320 

Type TD, Form G 321 

Form L ; 321 

Form R 321 

Relay Contacts, Adjustment of 322 

Resistance Measurement 322 

TA Form A 2 . 323 

Adjustment of A-C. Magnet Core. . . . . 327 

- Dashpot 323 

Floating Main Contacts 326 

Relay 327 

Setting Springs 329 

Springs 324 

Condensers 332 

Line Drop Compensation 329 

Locating Trouble 331 

Arcing at Relay Contacts 332 

Error Due to Compensating Winding . . . 332 

Error in Voltage 332 

Failure to Build Up 331 

Fall in Voltage 331 

Fluctuating Voltage 331 

TA Form F 333 

Adjustment of A-C. Magnet Core 337 

Dashpot 333 

Floating Main Contacts 337 

Levers and Springs 333 

Relay 337 

Setting Relay Springs 338 

Condensers 338 

Locating Trouble 338 

TA Form K . . . 338 

Form L 333 

TD Form L 340 

Form R 341 

Adjustment of Main Control Magnet. . . 341 

Adjustment of Relay Magnet 341 

Form S 340 

FormT 340 

Form W (Speed Regulator) 342 

RELAYS, RAILWAY 372 

482 



Subject Page 
RESISTANCE: 

Armature 112 

Svn. Converter 190 

Field." 112 

Insulation 112 

Measurements (See also Instruments) 36 

Of Transformers, Cold 386 

Temperature Rise by 112 

REVERSED SERIES FIELD, TEST FOR 138 

RHEOSTAT DATA, D-C. GENERATOR 145 

RHEOSTATS: 

Field (in Testing Dept.) 23 

Field, Testing of 343 

Field, for Split Pole Syn. Converter 344 

Hand Operated Starting and Regulating 344 

For Projectors 377 

RISE BY RESISTANCE FORMULAE, TEMPER- 

TURE 112, 399 

ROLLER BEARINGS 89 

ROPES, SAFE LOADS ON 60 

ROTARY CONVERTERS (See Converters, Syn.) 

RUNNING LIGHT CORE LOSS 122 

On Various Types of Machines (See Machine 
Tvpe Heading) 

RUNNING TORQUE ON SYN. MOTORS 188 

SAFE LOADS: 

On Eyebolts 60 

On Manila Ropes and Slings 59 

On Ropes and Chains 60 

On Wire Cable or Slings 59 

SAFETY DEVICES 13 

SATURATION: 

Generator 120 

Motor. . . 120 

On Various Types of Machines (See Machine 

Type Heading) 

On Railway Contactors 367 

SCALES 26 

SEARCHLIGHTS (See Projectors) 

SERIES WOUND D-C. GENERATOR: 

Series Characteristic 140 

Shifting Brushes on 137 

SERIES AND RAILWAY MOTORS (D-C.) 163 

SERIES LIGHTING TRANSFORMERS 419 

SERVICE HEAT RUNS (ELECTRIC LOCO- 
MOTIVES) 303 

SETS: 

Loading 142 

Measuring ' 6 

Motor-Generator, Shop 7 

SHAFTS 79 

483 



Subject P AGE 
SHIFTING BRUSHES: 

On Comm. Pole D-C. Generators , 151 

On Non-Comm. Pole D-C. Generators. 137 

On Series Generators 140 

On Non-Comm. Pole D-C. Motors 157 

SHIFTING PHASES (TO LOAD A-C. GENER- 
ATORS)' 177 

SHORT-CIRCUIT RUN (A-C. GENERATORS)... 179 
SHUNT ADJUSTMENT (See Adjustment) 

SHUNT REGULATION (D-C. GENERATOR) 145 

SHUNTS: 

Grid, Position of 152 

Inductive 152 

SHUTTING DOWN STEAM TURBINE SETS. ... 272 

SIGNAL APPARATUS . 380 

SLIDE WIRE BRIDGE 38 

SLINGS, SAFE LOAD ON 59 

SLIP: 

Indicator 27 

Of Induction Motors 217 

SPACING: 

Brushes 83 

Commutating Poles 149 

SPARKING CHART '. 138 

SPECIAL INSTRUCTIONS, STEAM TURBINES. 233 
SPECIAL TESTS ON VARIOUS TYPES OF MA- 
CHINES (See Machine Type Heading) 
SPEED: 

And Frequency ' 32 

Curve, D-C. Motors, Hot 159 

Railway Motors 165 

Railway Contactors 368 

Indicators 33 

Limiting Device, Adjustment of 113 

Regulation, Non-Comm. Pole D-C. Motors 158 

Variation, Comm. Pole D-C. Motors 161 

SPLIT POLE SYN. CONVERTERS (See Converters) 

STABILITY TEST ON EXCITERS : . . 153 

STAGE VALVES 265 

STANDARD EFFICIENCY ON VARIOUS TYPES 

OF MACHINES (See Machine Type Heading) 
STANDARD TESTS, METHODS OF CONDUCT- 
ING 108-135 

Armatures, Stationary Tests on 108 

Core Loss, Belted 123 

Deceleration 128 

Running Light 122 

Drop on Spools 

Limits of Variation in Ill 

Numbering Spools 112 

End Play Device, Magnetic 117 

Mechanical 118 

484 



Subject Page 
STANDARD TESTS, METHODS OF CONDUCT- 
ING— Cont'd 

High Potential 113 

Input-Output 130 

Load Loss 132 

Maximum Output 134 

Overspeed Test 135 

Polarity Ill 

Potential Curve Between Brushes 135 

Resistance 112 

Armature 112 

Insulation 112 

Shunt and Series Fields 112 

Temperature Rise by 112 

Saturation 120 

Generator 120 

Motor 120 

Speed Limiting Device, Adjustment of 113 

Wave Form — Potential Curve Between Brushes . 135 

STANDS, FLOOR 14 

STARTERS, AUTOMATIC 344 

STARTING TEST: 

Induction Motor 222 

Synchronous Converter, A-C 198 

Synchronous Converter, D-C 198 

Svnchronous Motor 185 

STARTING UP: 

General Instructions on 100 

D-C. Motor 157 

Marine Engines 293 

Synchronous Converter (from A-C. End) 193 

Svnchronous Motors 183 

STATIC TEST (A-C. GENERATOR) 182 

STATIONARY APPARATUS 105 

STATIONARY TORQUE: 

On Syn. Motor 188 

Recorder 29 

STEAM CONSUMPTION TESTS: 

On Turbines (See Turbines) 274 

On Marine Engines 294 

STEAM: 

Engine Indicator 26 

Power 10 

Turbines (See Turbines) 

Turbine Generators (See Turbines) 

STEP BEARING 238 

STORAGE BATTERY LOCOMOTIVES 355 

STRAINERS (AIR BRAKE APPARATUS) 361 

STRAY FIELDS, TEST FOR. . . 47 

STRESSES DUE TO ANGLE OF SLINGS 58 

STRING BRAKE METHOD FOR INPUT-OUT- 
PUT ON INDUCTION MOTORS 223 

485 



Subject , p AG e 

STUD POTENTIAL CURVE, D-C. GENERATOR 147 

SWITCHBOARDS 14 

SWITCHES: 

MS 363 

MU Tripping 364 

SYNCHRONOUS CONVERTERS (See Converters) 

SYNCHRONOUS IMPEDANCE 172 

On Various Machines (See Machine Type Heading) 
SYNCHRONOUS MOTORS (See Motors, Synchro- 
nous) 

TA FORM A 2 (VOLTAGE REGULATOR) 323 

Form F (Voltage Regulator) 333 

Form K (Voltage Regulator) 338 

Form L (Voltage Regulator) 333 

TABLES, TESTING 19 

TACHOMETERS ; 32 

TAPS: 

Transformers 392 

Starting Compensators 347 

TD FORM L (VOLTAGE REGULATOR) 340 

Form R 341 

Form S 340 

Form T 340 

Form W 342 

TEMPERATURE: 

Coils : 103 

Rise of Bearings 88, 103 

Rise on Heat Runs 103 

Rise, Formula for 112, 399 

TERMINAL BOARD (A-C. GENERATOR) 173 

TESTING: 

Records 106, 107 

Sets (High Potential) 

TEST REPORT 107 

TEST TRACKS (GENERAL ELECTRIC) 300, 304 

Electric Locomotives 300 

Friction by Free Running 304 

Friction from Coasting 304 

Mounting Motors on Trucks 302 

Operating Rules 304 

Order of Tests 300 

Pull Curve 302 

Service Heat Runs 303 

Trolley Bases 302 

Train Friction ■. 303 

THERMAL CHARACTERISTICS (RAILWAY 

MOTORS) 165 

THERMOMETERS: 

Placing of 101 

Reading of, During Heat Runs 144, 14o 

486 



Subject Page 

THOMSON BRIDGE 40 

THREE-WIRE: 

Balancer Sets 154 

D-C. Generators, Comm. Pole 153 

Xon-Comm. Pole 147 

THRUST BEARINGS 88 

For Turbines 251 

TIME-CURRENT CURVE (RAILWAY FUSES) ... 369 
TORQUE: 

Formulae for 220 

On Induction Motors, Stationary 220 

On Synchronous Motors 188 

Recorder, Stationary 29 

TRACTIVE EFFORT 169 

TRAIN CONTROL APPARATUS 360-372 

Air Brake Apparatus 360 

Air Valves 360 

Governors : 361 

Strainers 361 

Circuit Breakers (Railway) 371 

Connection Boxes 364 

Contactors (Railway) 364 

Finger Pressure 366 

Heat Runs 368 

Life Tests 368 

Minimum Pick Up 366 

Pull Curves, A-C 367 

D-C 367 

Saturation Curve 367 

Speed Curve 368 

Wipe 366 

Work Curve . ■ 368 

Contactor Boxes 370 

Controllers 361 

Automatic and Semi- Automatic 362 

Pilot Valves for 363 

Couplers 370 

Cutouts 364 

Fuses 369 

Time-Current Curve 369 

Fuse Boxes 369 

Inspection and High Potential Tests 360 

Jumpers 371 

MS Switches 363 

MU Tripping Switches 364 

Relavs (Railway) 372 

TRAIN FRICTION 303 

TRAMMEL 152 

TRANSFORMERS: 

Current 50 

Potential 48 



4.S 



Subject p AGE 
TRANSFORMERS— Cont'd 

Power (See Transformer Tests) 

Shop ' 23 

TRANSFORMER TESTS 384-420 

Constant Potential 384 

Commercial Tests 384 

Complete Test 384 

Core Loss and Exciting Current 393 

Efficiency 384 

Calculation of 404 

Exciting Current 393 

Failures in Test 404 

Heat Run 395 

High Potential 400 

Impedance 393 

Induced Voltage 403 

Insulation Tests 384 

Order of Tests 385 

Phase Rotation 390 

Polarity 386 

Preparation for Test 385 

Ratio 391 

Regulation . 384 

Calculation of 405 

Resistance, Cold 386 

Taps, Checking 392 

Types of 384 

Air Blast 384 

Natural Draft ? 384 

Oil-Cooled 384 

Water- and Oil-Cooled 385 

Reactances 418 

Tests Required 419 

Double or Triple Voltage 419 

Heat Run 419 

High Potential 419 

Impedance 419 

Resistance, Cold 419 

Regulators, Induction 406 

Type BR 414 

Tests Required 415 

Auxiliary Apparatus 418 

Core Loss 415 

Heat Run 416 

High Potential 418 

Impedance 416 

Induced Voltage 418 

Ratio 415 

Resistance, Cold 415 

Polyphase 410 

Tests Required 411 

488 



Subject Page 
TRANSFORMER TESTS— Cont'd 
Regulators, Induction 

Auxiliary Apparatus 414 

Core Loss 412 

Heat Run 412 

Polyphase 

Tests Required 

High Potential 413 

Impedance 412 

Induced Voltage 414 

Noise Test 414 

Ratio and Polarity 411 

Resistance, Cold 411 

Single-Phase 406 

Tests Required 407 

Auxiliary Apparatus 409 

Core Loss 408 

Heat Run 408 

High Potential 408 

Impedance 408 

Induced Voltage 409 

Noise Test 409 

Polarity 407 

Ratio 407 

Resistance, Cold 407 

Series Lighting 419 

TRIP RIGGING, EMERGENCY, FOR TUR- 
BINES 241 

TROLLEY BASES (ELECTRIC LOCOMOTIVES) 302 

TRUCKLIGHT CONTROLLER 380 

TRUING COMMUTATORS 95 

TUBES, APPLYING HIGH POTENTIAL TO 359 

TURBINES, STEAM 227-284 

Bafflers 238, 263 

Balance, Field 246 

Wheel 243 

Bearings, Thrust 251 

Commercial Test 227 

Defects 273 

Generators 265 

Tests 269 

Alternators 269 

*' Motoring" 272 

Record Sheets 273 

Resistance, Cold 269 

Shutting Down 272 

Ventilation 273 

Zero Excitation Heat Run 272 

D-C. Generators 273 

Governor Tests, Emergency 247 

Operating .' 251 

Instruments 233 

489 



Subject P AGE 
TURBINES, STEAM— Cont'd 

Nomenclature 227 

Piping, Steam, Exhaust and Oil ; 232 

Preparing for Test 233 

Oil Flow 235 

Packing Rings, Carbon 241 

Step Bearing 238 

Trip Rigging 241 

Water Leaks 233 

Special Instructions 233 

Special Tests 232 

Steam Consumption Test 274 

Arrangement of Apparatus 283 

Auxiliary Pumps 284 

Cautions 284 

Equipment, Electrical 284 

Steam Controlling 283 

Assembly 274 

Loading . . : 279 

Water Brake 280 

Preparation for Test 274 

Readings ,. . . . 275 

Flow 279 

Tanks 279 

Pressure 275 

Temperature 278 

Tests 281 

Bowl Pressure Curve 283 

Load Curve 282 

Maximum Load, Non-Condensing 282 

No-Load Flow 282 

Shell Pressure Curve 283 

Speed Curve 282 

Superheat Curve 283 

Vacuum Curve 282 

Valves, Stage 265 

TURBO-ALTERNATORS (See Turbines) 

TYPES OF TRANSFORMERS 384 

UNBALANCED READINGS, (3-WIRE GENER- 
ATORS) 149 

U-TUBES 26, 277 

VACUUM GAUGE 27 

VALVES: 

For Marine Engines 293 

For Railway Controllers, Pilot 363 

Stage 265 

VARIABLE SPEED D-C. MOTORS 162 

VENTILATION TESTS: 

D-C. Motors 171 

Turbine Sets ■ 273 

490 



Subject • Page 

VOLTAGE RANGE CURVES (SPLIT POLE SYN. 

CONVERTERS) 204 

VOLTAGE: 

Ratio (Synchronous Converter) 191 

Regulation (See Regulation) 

Regulators (See Regulators) 

VOLTMETERS 45 

Calibration Constant 46 

Milli 46 

WATER BOXES 21, 176 

WATER-BRAKE, USE OF 280 

WATER RATE (See Steam Consumption) 

WATTMETERS 51 

Correction for Phase Angle 55 

WAVE FORM: 

Potential Curve between Brushes 134 

A-C. Generators 182 

WAVE SHAPES 34 

WEIGHTS OF VARIOUS MATERIALS 62 

WHEATSTONE BRIDGE 37 

WHEEL BALANCE, STEAM TURBINES 243 

WINDING DEVICES (MINING LOCOMOTIVES) 354 

WIPE (RAILWAY CONTACTORS) 366 

WIRING 98 

Motor Fields 99 

Transformers 100 

Svnchronous Converters 193 

WORK CURVE (RAILWAY CONTACTORS) 368 

ZERO EXCITATION HEAT RUN (STEAM TUR- 
BINE GENERATOR) 272 

ZERO POWER-FACTOR HEAT RUN 180 



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